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Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 62 (from laksa146)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa062.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://www.britannica.com/science/antidepressant\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.britannica.com/science/antidepressant\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.britannica.com\/science\/antidepressant","crawl_time":1775699191,"first_indexed_time":1519078873,"http_code":200,"src_unparsed":"com,britannica!www,\/science\/antidepressant s443","src_root_hash":"5455945239613777662","history_drop_reason":null,"meta_title":"Antidepressant | Mental Health Benefits | Britannica","meta_descriptions":["Antidepressant, any member of a class of drugs prescribed to relieve depression. There are several major classes of antidepressant drugs, the best known of which include the tricyclic antidepressants, monoamine oxidase inhibitors (MAOIs), and selective serotonin reuptake inhibitors (SSRIs). Other"],"attrs_boilerpipe_text":"News\n•\ndepression\n,  in\npsychology\n, a mood or emotional state that is marked by feelings of low self-worth or guilt and a reduced ability to enjoy life. A person who is depressed usually experiences several of the following symptoms: feelings of sadness, hopelessness, or pessimism; lowered\nself-esteem\nand heightened self-depreciation; a decrease or loss of ability to take pleasure in ordinary activities; reduced energy and vitality; slowness of thought or action; loss of\nappetite\n; and disturbed\nsleep\nor\ninsomnia\n.\nDepression differs from simple grief or mourning, which are appropriate emotional responses to the loss of loved persons or objects. Where there are clear grounds for a person’s unhappiness, depression is considered to be present if the depressed mood is disproportionately long or severe vis-à-vis the precipitating event. The distinctions between the duration of depression, the circumstances under which it arises, and certain other characteristics underlie the classification of depression into different types. Examples of different types of depression include\nbipolar disorder\n,\nmajor depressive disorder\n(clinical depression),\npersistent depressive disorder\n, and\nseasonal affective disorder\n.\nCharacteristics and causes of depression\nDepression is probably the most common psychiatric complaint and has been described by physicians since before the time of ancient Greek physician\nHippocrates\n, who called it\nmelancholia\n. The course of the disorder is extremely variable from person to person; it may be mild or severe,\nacute\nor chronic. Untreated, depression may last an average of four months or longer. Depression is twice as prevalent in women than in men. The typical age of onset is in the 20s, but it may occur at any age.\nBritannica Quiz\n44 Questions from Britannica’s Most Popular Health and Medicine Quizzes\nDepression can have many causes. Unfavorable life events can increase a person’s vulnerability to depression or trigger a depressive episode. Negative thoughts about oneself and the world are also important in producing and maintaining depressive symptoms. However, both psychosocial and biochemical mechanisms seem to be important causes; the chief biochemical cause appears to be the defective regulation of the release of one or more naturally occurring\nneurotransmitters\nin the\nbrain\n, particularly\nnorepinephrine\nand\nserotonin\n. Reduced quantities or reduced activity of these chemicals in the brain is thought to cause the depressed mood in some sufferers.\nDepression is also associated with disordered\nrapid eye movement (REM) sleep\n. A region of the brain known as the\namygdala\ncontains\nneurons\nthat project into the\nbrainstem\nand appear to be involved in modulating REM sleep. The amygdala is also associated with processing negative thoughts and may be enlarged, hyperactive, or otherwise dysfunctional in some depressed persons. Although the significance of these associations is\nyet\nto be defined, the link between depression, disordered REM sleep, and abnormalities of the amygdala has led to new avenues of research into the neurobiology and treatment of depression.\nResearch suggests that depression is also linked to\nphysical activity\n, whereby physical activity may lower a person’s risk of developing depression. Individuals who\nexercise\ntypically report better\nmental health\nand are less likely to be depressed, compared with individuals who do not exercise.\nTypes of depression\nBipolar disorder\n, major depressive disorder, and persistent depressive disorder are the primary types of depression. A person who experiences alternating states of depression and\nmania\n(abnormal elevation of mood) or hypomania (distinct, though not necessarily abnormal, elevation of mood) is said to suffer from bipolar disorder.\nMajor depressive disorder\nis\ncharacterized\nby severe symptoms that disrupt the individual’s daily life, typically with effects on appetite, sleep, work, or the ability to enjoy life. Episodes of major depression can occur at any age and may occur once or multiple times in an affected person’s life.\nPersistent depressive disorder\ninvolves symptoms that last two or more years, sometimes marked by episodes of major depression.\nSmart, reliable knowledge for professionals, students, and curious minds everywhere.\nSUBSCRIBE\nOther types of depression include postpartum depression, psychotic depression, and seasonal affective disorder, each of which develops under specific circumstances.\nPostpartum depression\ndevelops in women in the period following\nchildbirth\n. Symptoms include\nanxiety\n, a lack of interest in caring for the infant, and feelings of sadness, hopelessness, or inadequacy. Postpartum depression is longer-lasting and more severe than the “baby blues,” a common condition among women after childbirth that typically involves mood swings, feelings of sadness, and crying spells.\nPsychotic depression arises against a background of\npsychosis\n, which may involve symptoms of\ndelusions\n, hallucinations, or\nparanoia\n.\nSeasonal affective disorder\nis characterized by the onset of depressive symptoms in autumn and winter, which are\nalleviated\nwith increased exposure to natural light in spring and summer.\nTreatments for depression\nThere are three main treatments for depression. The two most important—and widespread by far—are\npsychotherapy\nand psychotropic\nmedication\n, specifically\nantidepressants\nsuch as\nbupropion\n. Psychotherapy aims to alter the patient’s maladaptive\ncognitive\nand behavioral responses to stressful life events while also giving emotional support to the patient. Antidepressant medications, by contrast, directly affect the chemistry of the brain and presumably achieve their therapeutic effects by correcting the chemical dysregulation that is causing the depression. Two types of medications,\ntricyclic antidepressants\nand\nselective serotonin reuptake inhibitors\n(SSRIs; e.g., fluoxetine [\nProzac\n]), though chemically different, both serve to prevent the presynaptic reuptake of serotonin (and in the case of tricyclic antidepressants, norepinephrine as well). This results in the buildup or accumulation of neurotransmitters in the brain and allows them to remain in contact with the\nnerve cell\nreceptors longer, thus helping to elevate the patient’s mood. By contrast, the antidepressants known as\nmonoamine oxidase inhibitors\n(MAOIs) interfere with the activity of monoamine oxidase, an\nenzyme\nthat is known to be involved in the breakdown of norepinephrine and serotonin.\nIn cases of severe depression in which therapeutic results are needed quickly,\nelectroconvulsive therapy\n(ECT) has sometimes proved helpful. In this procedure, a convulsion is produced by passing an\nelectric current\nthrough the person’s brain. For most persons with depression, however, the best therapeutic results are obtained by using a combination of psychotherapy and\nantidepressant\nmedication. (\nSee also\ntherapeutics\n.)\nSome persons with depression are affected by\ntreatment-resistant depression (TRD), meaning that they are refractory to existing therapies. For those individuals, scientists have been investigating\nalternative\ntherapeutic approaches, including\ndeep brain stimulation\n(DBS) and\ngene therapy\n. In DBS, experimental research has focused on the implantation of an electrode in a region of the brain known as the nucleus accumbens, which is located in the striatum (neostriatum) deep within the\ncerebral\nhemispheres and is associated with emotions and feelings such as fear, pleasure, and reward. Studies of depressed animals and postmortem studies of the brains of patients with depression have revealed that reduced levels of a protein known as p11 in cells of the nucleus accumbens are associated with depression. In depressed animals, increasing p11 levels in the nucleus accumbens using gene therapy has been found to relieve depression-like symptoms. Both DBS and gene therapy, however, are associated with potentially dangerous side effects.\nThis article was most recently revised and updated by\nMichael Ray\n.","attrs_markdown":"[![Encyclopedia Britannica](https:\/\/cdn.britannica.com\/mendel\/eb-logo\/MendelNewThistleLogo.png)](https:\/\/www.britannica.com\/)\n\n[![Encyclopedia Britannica](https:\/\/cdn.britannica.com\/mendel\/eb-logo\/MendelNewThistleLogo.png)](https:\/\/www.britannica.com\/)\n\n[SUBSCRIBE](https:\/\/premium.britannica.com\/premium-membership\/?utm_source=premium&utm_medium=global-nav&utm_campaign=blue-evergreen)\n\n[SUBSCRIBE](https:\/\/premium.britannica.com\/premium-membership\/?utm_source=premium&utm_medium=global-nav-mobile&utm_campaign=blue-evergreen)\n\nLogin\n\nhttps:\/\/premium.britannica.com\/premium-membership\/?utm\\_source=premium\\&utm\\_medium=nav-login-box\\&utm\\_campaign=evergreen\n\n[SUBSCRIBE](https:\/\/premium.britannica.com\/premium-membership\/?utm_source=premium&utm_medium=hamburger-menu&utm_campaign=blue)\n\n[Ask the Chatbot](https:\/\/www.britannica.com\/chatbot)\n\n[Games & Quizzes](https:\/\/www.britannica.com\/quiz\/browse) [History & Society](https:\/\/www.britannica.com\/History-Society) [Science & Tech](https:\/\/www.britannica.com\/Science-Tech) [Biographies](https:\/\/www.britannica.com\/Biographies) [Animals & Nature](https:\/\/www.britannica.com\/Animals-Nature) [Geography & Travel](https:\/\/www.britannica.com\/Geography-Travel) [Arts & Culture](https:\/\/www.britannica.com\/Arts-Culture) [ProCon](https:\/\/www.britannica.com\/procon) [Money](https:\/\/www.britannica.com\/money) [Videos](https:\/\/www.britannica.com\/videos)\n\n[antidepressant](https:\/\/www.britannica.com\/science\/antidepressant)\n\n[Introduction](https:\/\/www.britannica.com\/science\/antidepressant)   [References & Edit History](https:\/\/www.britannica.com\/science\/antidepressant\/additional-info)  [Quick Facts & Related Topics](https:\/\/www.britannica.com\/facts\/antidepressant)\n\n[Images](https:\/\/www.britannica.com\/science\/antidepressant\/images-videos)\n\n[![Prozac](https:\/\/cdn.britannica.com\/50\/123550-004-4E7CBC62\/Prozac-pills.jpg)](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg)\n\nAt a Glance\n\n[![Prozac](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg?w=200&h=200&c=crop)](https:\/\/www.britannica.com\/summary\/antidepressant)\n\n[antidepressant summary](https:\/\/www.britannica.com\/summary\/antidepressant)\n\n![Britannica AI Icon](https:\/\/cdn.britannica.com\/mendel-resources\/3-178\/images\/chatbot\/star-ai.svg?v=3.178.5)\n\nContents\n\nAsk Anything\n\n[Health & Medicine](https:\/\/www.britannica.com\/browse\/Health-Medicine)    [Medicine](https:\/\/www.britannica.com\/browse\/Medicine)\n\nCITE\n\nShare\n\nFeedback\n\nExternal Websites\n\n[![Prozac](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg?w=400&h=300&c=crop)](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg)\n\n[Prozac](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg) Prozac pills.\n\n(more)\n\n# antidepressant\nHomework Help\n\nAlso known as: antidepressant drug, psychic energizer\n\nWritten by\n\n[Floyd E. Bloom Chairman, Department of Neuropharmacology, Scripps Research Institute, La Jolla, California. Editor in Chief, *Science* magazine. Coauthor of *Biochemical Basis of Neuropharmacology* and...](https:\/\/www.britannica.com\/contributor\/Floyd-E-Bloom\/307)\n\nFloyd E. Bloom\n\nFact-checked by\n\n[Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....](https:\/\/www.britannica.com\/editor\/The-Editors-of-Encyclopaedia-Britannica\/4419)\n\nBritannica Editors\n\nLast updated\n\nMar. 21, 2026\n\n•[History](https:\/\/www.britannica.com\/science\/antidepressant\/additional-info#history)\n\n![Britannica AI Icon](https:\/\/cdn.britannica.com\/mendel-resources\/3-178\/images\/chatbot\/star-ai.svg?v=3.178.5) Britannica AI\n\nAsk Anything\n\nTable of Contents\n\nTable of Contents\n\nAsk Anything\n\n## News •\n[No evidence for psychedelics and depression despite 'hype'](https:\/\/www.abc.net.au\/news\/science\/2026-03-19\/psychedlics-may-be-no-better-than-antidepressants-for-depression\/106467464)  • Mar. 18, 2026, 1:30 PM ET (ABC News (Australia))\n\nShow less\n\nTop Questions\n\n- What is an antidepressant?\n- Why are antidepressants used?\n- How do antidepressants help with depression?\n- Are there different types of antidepressants?\n- What are some possible side effects of antidepressants?\n- How do doctors decide which antidepressant is best for a patient?\n\nShow more\n\nShow less\n\n**antidepressant**, any member of a class of [drugs](https:\/\/www.britannica.com\/science\/drug-chemical-agent) prescribed to relieve [depression](https:\/\/www.britannica.com\/science\/depression-psychology). There are several major classes of antidepressant drugs, the best known of which include the tricyclic antidepressants, [monoamine oxidase inhibitor](https:\/\/www.britannica.com\/science\/monoamine-oxidase-inhibitor)s (MAOIs), and selective [serotonin](https:\/\/www.britannica.com\/science\/serotonin) reuptake inhibitors ([SSRI](https:\/\/www.britannica.com\/science\/selective-serotonin-reuptake-inhibitor)s). Other important groups include the [norepinephrine](https:\/\/www.britannica.com\/science\/epinephrine) reuptake inhibitors (NRIs), the serotonin-norepinephrine reuptake inhibitors (SNRIs), and the [atypical](https:\/\/www.merriam-webster.com\/dictionary\/atypical) antidepressants, a [disparate](https:\/\/www.merriam-webster.com\/dictionary\/disparate) group of agents that possess unique structural features and mechanisms of action.\n\nChemically speaking, depression is apparently caused by reduced quantities or reduced activity of the monoamine [neurotransmitters](https:\/\/www.britannica.com\/science\/neurotransmitter) (e.g., serotonin, norepinephrine, and [dopamine](https:\/\/www.britannica.com\/science\/dopamine)) within the [brain](https:\/\/www.britannica.com\/science\/brain). This [etiology](https:\/\/www.merriam-webster.com\/dictionary\/etiology) is supported by evidence that drugs that restore chemical imbalances in the levels of neurotransmitters in the brain effectively [mitigate](https:\/\/www.merriam-webster.com\/dictionary\/mitigate) symptoms of depression. All antidepressants, in fact, achieve their effects by [inhibiting](https:\/\/www.merriam-webster.com\/dictionary\/inhibiting) the body’s reabsorption or inactivation of monoamine neurotransmitters, thus allowing the neurotransmitters to accumulate and remain in contact with their [receptors](https:\/\/www.britannica.com\/science\/receptor-nerve-ending) for prolonged periods of time; these changes seem to be important in elevating mood and relieving depression.\n\nOne of the first antidepressants to demonstrate success clinically was [iproniazid](https:\/\/www.britannica.com\/science\/iproniazid), a [drug](https:\/\/www.britannica.com\/science\/drug-chemical-agent) developed originally for the [treatment](https:\/\/www.britannica.com\/science\/therapeutics) of [tuberculosis](https:\/\/www.britannica.com\/science\/tuberculosis). In the 1950s scientists discovered that the extreme euphoria and hyperactivity experienced by some patients who were taking iproniazid was caused by the drug’s inhibition of monoamine oxidase, an [enzyme](https:\/\/www.britannica.com\/science\/enzyme) in the [liver](https:\/\/www.britannica.com\/science\/liver) and brain that normally breaks down the monoamine neurotransmitters. Drugs that were better at blocking the activity of this enzyme were even more effective in evoking euphoria. As a group, these drugs came to be known as MAOIs.\n\n[![Prozac](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg) More From Britannica therapeutics: Antidepressant drugs](https:\/\/www.britannica.com\/science\/therapeutics\/Psychotherapy#ref294028)\n\nAlso in the 1950s the first [tricyclic antidepressants](https:\/\/www.britannica.com\/science\/tricyclic-antidepressant-drug) were discovered. These agents, so called because they are composed chemically of three [carbon](https:\/\/www.britannica.com\/science\/carbon-chemical-element) rings, [inhibit](https:\/\/www.merriam-webster.com\/dictionary\/inhibit) the active reuptake, to varying degrees, of norepinephrine, serotonin, and dopamine in the brain. The tricyclics include [imipramine](https:\/\/www.britannica.com\/science\/imipramine), [amitriptyline](https:\/\/www.britannica.com\/science\/amitriptyline), [desipramine](https:\/\/www.britannica.com\/science\/desmethylimipramine), nortriptyline, and a number of other [compounds](https:\/\/www.merriam-webster.com\/dictionary\/compounds). These drugs relieve symptoms in a high proportion (more than 70 percent) of depressed patients. As with the MAOIs, the antidepressant action of tricyclic drugs may not become apparent until two to four weeks after treatment begins.\n\n[SSRI](https:\/\/www.britannica.com\/science\/selective-serotonin-reuptake-inhibitor)s were introduced in the 1980s, and shortly thereafter they became some of the most commonly used antidepressants, primarily because they have fewer side effects than [tricyclic](https:\/\/www.britannica.com\/science\/tricyclic-antidepressant-drug)s or MAOIs. SSRIs include fluoxetine ([Prozac](https:\/\/www.britannica.com\/science\/Prozac)), paroxetine (Paxil), and sertraline (Zoloft). SSRIs are also used in the treatment of [anxiety](https:\/\/www.britannica.com\/science\/anxiety), [eating disorders](https:\/\/www.britannica.com\/science\/eating-disorder), [panic disorder](https:\/\/www.britannica.com\/science\/panic-disorder), [obsessive-compulsive disorder](https:\/\/www.britannica.com\/science\/obsessive-compulsive-disorder), and [borderline personality disorder](https:\/\/www.britannica.com\/science\/borderline-personality-disorder).\n\nOther antidepressants inhibit the reuptake of monoamine neurotransmitters in variable amounts. For example, the SNRI venlafaxine blocks both serotonin and norepinephrine reuptake; therapeutic doses of the drug, however, also weakly inhibit dopamine reuptake. Nefazodone, an atypical antidepressant, [inhibits](https:\/\/www.merriam-webster.com\/dictionary\/inhibits) serotonin and norepinephrine reuptake and is an [antagonist](https:\/\/www.merriam-webster.com\/dictionary\/antagonist) at certain serotonin receptors and at α1\\-adrenoceptors.\n\nThree to four weeks are typically required to produce significant improvement in individuals who are taking antidepressant medications. Most physicians recommend that patients continue to take antidepressants for at least six months to prevent a relapse. The type of antidepressant that a physician prescribes depends largely on symptoms and severity of the condition and on the patient’s tolerance of side effects. For instance, the MAOIs—chiefly isocarboxazid, phenelzine, and tranylcypromine—in general are used only after treatment with tricyclic drugs has proved unsatisfactory, because these drugs’ side effects are unpredictable and their complex interactions are incompletely understood. Fluoxetine often relieves cases of depression that have failed to yield to tricyclics or MAOIs.\n\nRelated Topics:\n\n[bupropion](https:\/\/www.britannica.com\/science\/bupropion)\n\n[trazodone](https:\/\/www.britannica.com\/topic\/trazodone)\n\n[tricyclic antidepressant drug](https:\/\/www.britannica.com\/science\/tricyclic-antidepressant-drug)\n\n[selective serotonin reuptake inhibitor](https:\/\/www.britannica.com\/science\/selective-serotonin-reuptake-inhibitor)\n\n[monoamine oxidase inhibitor](https:\/\/www.britannica.com\/science\/monoamine-oxidase-inhibitor)\n\n*(Show more)*\n\n[See all related content](https:\/\/www.britannica.com\/facts\/antidepressant)\n\nExplore Britannica Premium\\!\n\nGo beyond the basics with trusted, in-depth knowledge for professionals, students, and lifelong learners.\n\n[SUBSCRIBE](https:\/\/premium.britannica.com\/premium-membership\/?utm_source=premium&utm_medium=inline-cta&utm_campaign=basics-2026)\n\n![Penguin, ship, mountain, atlas](https:\/\/cdn.britannica.com\/marketing\/inline-left.webp)\n\n![shohei ohtani, plants, andy wharhol art](https:\/\/cdn.britannica.com\/marketing\/inline-right.webp)\n\n![Mobile](https:\/\/cdn.britannica.com\/marketing\/inline-mobile.webp?w=400)\n\nSide effects vary among the types of antidepressants and may include sleepiness, tremors, [anxiety](https:\/\/www.britannica.com\/science\/anxiety), loss of sexual desire, and [nausea](https:\/\/www.britannica.com\/science\/nausea-pathology). The possible side effects of tricyclics specifically include dry mouth, blurred [vision](https:\/\/www.britannica.com\/science\/vision-physiology), [constipation](https:\/\/www.britannica.com\/science\/constipation), dizziness, and difficulty in [urination](https:\/\/www.britannica.com\/science\/urination). [Cerebral](https:\/\/www.merriam-webster.com\/dictionary\/Cerebral) and cardiac toxicity have been observed in some individuals. In rare instances, antidepressants may cause life-threatening side effects. For instance, nefazodone is associated with a low risk of death from hepatic (liver) failure; the discovery of this risk association resulted in the drug’s discontinuation in the [United States](https:\/\/www.britannica.com\/place\/United-States). Many antidepressants also have the potential to produce dangerous drug interactions. This is especially true of MAOIs; the interaction of these drugs with tyramine, which is found in many foods as well as in [wine](https:\/\/www.britannica.com\/topic\/wine) and certain types of [beer](https:\/\/www.britannica.com\/topic\/beer), can cause [hypertension](https:\/\/www.britannica.com\/science\/hypertension) (high [blood pressure](https:\/\/www.britannica.com\/science\/blood-pressure)) and severe [headache](https:\/\/www.britannica.com\/science\/headache).\n\n[Floyd E. Bloom](https:\/\/www.britannica.com\/contributor\/Floyd-E-Bloom\/307) [The Editors of Encyclopaedia Britannica](https:\/\/www.britannica.com\/editor\/The-Editors-of-Encyclopaedia-Britannica\/4419)\n\n![Britannica AI Icon](https:\/\/cdn.britannica.com\/mendel-resources\/3-178\/images\/chatbot\/star-ai.svg?v=3.178.5)Britannica AI\n\n*chevron\\_right*\n\nAntidepressant\n\n*close*\n\n[AI-generated answers](https:\/\/www.britannica.com\/about-britannica-ai) from Britannica articles. AI makes mistakes, so verify using Britannica articles.\n\n[depression](https:\/\/www.britannica.com\/science\/depression-psychology)\n\n- [Introduction](https:\/\/www.britannica.com\/science\/depression-psychology)\n- [Characteristics and causes of depression](https:\/\/www.britannica.com\/science\/depression-psychology#ref297878)\n- [Types of depression](https:\/\/www.britannica.com\/science\/depression-psychology#ref321576)\n- [Treatments for depression](https:\/\/www.britannica.com\/science\/depression-psychology#ref297879)\n\n[References & Edit History](https:\/\/www.britannica.com\/science\/depression-psychology\/additional-info)  [Quick Facts & Related Topics](https:\/\/www.britannica.com\/facts\/depression-psychology)\n\n[Images & Videos](https:\/\/www.britannica.com\/science\/depression-psychology\/images-videos)\n\n[![Prozac](https:\/\/cdn.britannica.com\/50\/123550-004-4E7CBC62\/Prozac-pills.jpg)](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg)\n\n[![Understanding seasonal affective disorder](https:\/\/cdn.britannica.com\/18\/188818-138-057CE8AE\/chemistry-seasonal-affective-disorder.jpg?w=400&h=225&c=crop)](https:\/\/www.britannica.com\/video\/chemistry-seasonal-affective-disorder\/-208059)\n\nAt a Glance\n\n[![default image](https:\/\/cdn.britannica.com\/mendel-resources\/3-178\/images\/shared\/new-thistle.svg?v=3.178.5)](https:\/\/www.britannica.com\/summary\/depression-psychology)\n\n[depression summary](https:\/\/www.britannica.com\/summary\/depression-psychology)\n\nQuizzes\n\n[![Encyclopaedia Britannica thistle graphic to be used with a Mendel\/Consumer quiz in place of a photograph.](https:\/\/cdn.britannica.com\/05\/215905-131-626D860A\/Encyclopaedia-Britannica-thistle-graphic-logo.jpg?w=200&h=200&c=crop)](https:\/\/www.britannica.com\/quiz\/44-questions-from-britannicas-most-popular-health-and-medicine-quizzes)\n\n[44 Questions from Britannica’s Most Popular Health and Medicine Quizzes](https:\/\/www.britannica.com\/quiz\/44-questions-from-britannicas-most-popular-health-and-medicine-quizzes)\n\n![Britannica AI Icon](https:\/\/cdn.britannica.com\/mendel-resources\/3-178\/images\/chatbot\/star-ai.svg?v=3.178.5)\n\nAsk Anything\n\nQuick Summary\n\n[Health & Medicine](https:\/\/www.britannica.com\/browse\/Health-Medicine)    [Conditions & Diseases](https:\/\/www.britannica.com\/browse\/Conditions-Diseases)    [Mental Disorders](https:\/\/www.britannica.com\/browse\/Mental-Disorders)\n\nCITE\n\nShare\n\nFeedback\n\nExternal Websites\n\n[![Prozac](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg?w=400&h=300&c=crop)](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg)\n\n[Prozac](https:\/\/cdn.britannica.com\/50\/123550-050-885369B3\/Prozac-pills.jpg) Prozac pills.\n\n(more)\n\n# depression\npsychology\n\nHomework Help\n\nAlso known as: mental depression\n\nWritten and fact-checked by\n\n[Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....](https:\/\/www.britannica.com\/editor\/The-Editors-of-Encyclopaedia-Britannica\/4419)\n\nBritannica Editors\n\n[History](https:\/\/www.britannica.com\/science\/depression-psychology\/additional-info#history)\n\n![Britannica AI Icon](https:\/\/cdn.britannica.com\/mendel-resources\/3-178\/images\/chatbot\/star-ai.svg?v=3.178.5) Britannica AI\n\nAsk Anything\n\nQuick Summary\n\nTable of Contents\n\nTable of Contents\n\nQuick Summary\n\nAsk Anything\n\n## News •\n[Fathers face rising depression risk a year after baby arrives](https:\/\/www.sciencedaily.com\/releases\/2026\/03\/260324230057.htm)\n\n• Mar. 24, 2026, 11:10 PM ET (ScienceDaily)\n\n...(Show more)\n\n[No evidence for psychedelics and depression despite 'hype'](https:\/\/www.abc.net.au\/news\/science\/2026-03-19\/psychedlics-may-be-no-better-than-antidepressants-for-depression\/106467464)  • Mar. 18, 2026, 1:30 PM ET (ABC News (Australia))\n\nShow less\n\n**depression**, in [psychology](https:\/\/www.britannica.com\/science\/psychology), a mood or emotional state that is marked by feelings of low self-worth or guilt and a reduced ability to enjoy life. A person who is depressed usually experiences several of the following symptoms: feelings of sadness, hopelessness, or pessimism; lowered [self-esteem](https:\/\/www.britannica.com\/dictionary\/self-esteem) and heightened self-depreciation; a decrease or loss of ability to take pleasure in ordinary activities; reduced energy and vitality; slowness of thought or action; loss of [appetite](https:\/\/www.britannica.com\/science\/appetite); and disturbed [sleep](https:\/\/www.britannica.com\/science\/sleep) or [insomnia](https:\/\/www.britannica.com\/science\/insomnia).\n\nIf you are experiencing a crisis or would like to speak with someone about depression, call the [National Suicide and Crisis Lifeline](https:\/\/988lifeline.org\/) at **988** or contact the [Crisis Text Line](https:\/\/www.crisistextline.org\/) by texting **HOME** to **741741**.\n\nDepression differs from simple grief or mourning, which are appropriate emotional responses to the loss of loved persons or objects. Where there are clear grounds for a person’s unhappiness, depression is considered to be present if the depressed mood is disproportionately long or severe vis-à-vis the precipitating event. The distinctions between the duration of depression, the circumstances under which it arises, and certain other characteristics underlie the classification of depression into different types. Examples of different types of depression include [bipolar disorder](https:\/\/www.britannica.com\/science\/bipolar-disorder), [major depressive disorder](https:\/\/www.britannica.com\/science\/major-depressive-disorder) (clinical depression), [persistent depressive disorder](https:\/\/www.britannica.com\/science\/dysthymic-disorder), and [seasonal affective disorder](https:\/\/www.britannica.com\/science\/seasonal-affective-disorder).\n\n## Characteristics and causes of depression\nDepression is probably the most common psychiatric complaint and has been described by physicians since before the time of ancient Greek physician [Hippocrates](https:\/\/www.britannica.com\/biography\/Hippocrates), who called it [melancholia](https:\/\/www.britannica.com\/science\/melancholia-psychology). The course of the disorder is extremely variable from person to person; it may be mild or severe, [acute](https:\/\/www.merriam-webster.com\/dictionary\/acute) or chronic. Untreated, depression may last an average of four months or longer. Depression is twice as prevalent in women than in men. The typical age of onset is in the 20s, but it may occur at any age.\n\n[![Encyclopaedia Britannica thistle graphic to be used with a Mendel\/Consumer quiz in place of a photograph.](https:\/\/cdn.britannica.com\/05\/215905-131-626D860A\/Encyclopaedia-Britannica-thistle-graphic-logo.jpg) Britannica Quiz 44 Questions from Britannica’s Most Popular Health and Medicine Quizzes](https:\/\/www.britannica.com\/quiz\/44-questions-from-britannicas-most-popular-health-and-medicine-quizzes)\n\nDepression can have many causes. Unfavorable life events can increase a person’s vulnerability to depression or trigger a depressive episode. Negative thoughts about oneself and the world are also important in producing and maintaining depressive symptoms. However, both psychosocial and biochemical mechanisms seem to be important causes; the chief biochemical cause appears to be the defective regulation of the release of one or more naturally occurring [neurotransmitters](https:\/\/www.britannica.com\/science\/neurotransmitter) in the [brain](https:\/\/www.britannica.com\/science\/brain), particularly [norepinephrine](https:\/\/www.britannica.com\/science\/norepinephrine) and [serotonin](https:\/\/www.britannica.com\/science\/serotonin). Reduced quantities or reduced activity of these chemicals in the brain is thought to cause the depressed mood in some sufferers.\n\nDepression is also associated with disordered [rapid eye movement (REM) sleep](https:\/\/www.britannica.com\/science\/rapid-eye-movement-sleep). A region of the brain known as the [amygdala](https:\/\/www.britannica.com\/science\/amygdala) contains [neurons](https:\/\/www.britannica.com\/science\/neuron) that project into the [brainstem](https:\/\/www.britannica.com\/science\/brainstem) and appear to be involved in modulating REM sleep. The amygdala is also associated with processing negative thoughts and may be enlarged, hyperactive, or otherwise dysfunctional in some depressed persons. Although the significance of these associations is [yet](https:\/\/www.britannica.com\/dictionary\/yet) to be defined, the link between depression, disordered REM sleep, and abnormalities of the amygdala has led to new avenues of research into the neurobiology and treatment of depression.\n\nResearch suggests that depression is also linked to [physical activity](https:\/\/www.britannica.com\/topic\/physical-activity), whereby physical activity may lower a person’s risk of developing depression. Individuals who [exercise](https:\/\/www.britannica.com\/topic\/exercise-physical-fitness) typically report better [mental health](https:\/\/www.britannica.com\/science\/mental-hygiene) and are less likely to be depressed, compared with individuals who do not exercise.\n\n## Types of depression\n[Bipolar disorder](https:\/\/www.britannica.com\/science\/bipolar-disorder), major depressive disorder, and persistent depressive disorder are the primary types of depression. A person who experiences alternating states of depression and [mania](https:\/\/www.britannica.com\/science\/mania) (abnormal elevation of mood) or hypomania (distinct, though not necessarily abnormal, elevation of mood) is said to suffer from bipolar disorder. [Major depressive disorder](https:\/\/www.britannica.com\/science\/major-depressive-disorder) is [characterized](https:\/\/www.britannica.com\/dictionary\/characterized) by severe symptoms that disrupt the individual’s daily life, typically with effects on appetite, sleep, work, or the ability to enjoy life. Episodes of major depression can occur at any age and may occur once or multiple times in an affected person’s life. [Persistent depressive disorder](https:\/\/www.britannica.com\/science\/dysthymic-disorder) involves symptoms that last two or more years, sometimes marked by episodes of major depression.\n\nExplore Britannica Premium\\!\n\nSmart, reliable knowledge for professionals, students, and curious minds everywhere.\n\n[SUBSCRIBE](https:\/\/premium.britannica.com\/premium-membership\/?utm_source=premium&utm_medium=inline-cta&utm_campaign=smart-2026)\n\n![Penguin, ship, mountain, atlas](https:\/\/cdn.britannica.com\/marketing\/inline-left.webp)\n\n![shohei ohtani, plants, andy wharhol art](https:\/\/cdn.britannica.com\/marketing\/inline-right.webp)\n\n![Mobile](https:\/\/cdn.britannica.com\/marketing\/inline-mobile.webp?w=400)\n\nOther types of depression include postpartum depression, psychotic depression, and seasonal affective disorder, each of which develops under specific circumstances. [Postpartum depression](https:\/\/www.britannica.com\/science\/postpartum-depression) develops in women in the period following [childbirth](https:\/\/www.britannica.com\/science\/birth). Symptoms include [anxiety](https:\/\/www.britannica.com\/science\/anxiety), a lack of interest in caring for the infant, and feelings of sadness, hopelessness, or inadequacy. Postpartum depression is longer-lasting and more severe than the “baby blues,” a common condition among women after childbirth that typically involves mood swings, feelings of sadness, and crying spells. Psychotic depression arises against a background of [psychosis](https:\/\/www.britannica.com\/science\/psychosis), which may involve symptoms of [delusions](https:\/\/www.merriam-webster.com\/dictionary\/delusions), hallucinations, or [paranoia](https:\/\/www.britannica.com\/science\/paranoia). [Seasonal affective disorder](https:\/\/www.britannica.com\/science\/seasonal-affective-disorder) is characterized by the onset of depressive symptoms in autumn and winter, which are [alleviated](https:\/\/www.merriam-webster.com\/dictionary\/alleviated) with increased exposure to natural light in spring and summer.\n\n## Treatments for depression\nThere are three main treatments for depression. The two most important—and widespread by far—are [psychotherapy](https:\/\/www.britannica.com\/science\/psychotherapy) and psychotropic [medication](https:\/\/www.britannica.com\/science\/drug-chemical-agent), specifically [antidepressants](https:\/\/www.britannica.com\/science\/antidepressant) such as [bupropion](https:\/\/www.britannica.com\/science\/bupropion). Psychotherapy aims to alter the patient’s maladaptive [cognitive](https:\/\/www.merriam-webster.com\/dictionary\/cognitive) and behavioral responses to stressful life events while also giving emotional support to the patient. Antidepressant medications, by contrast, directly affect the chemistry of the brain and presumably achieve their therapeutic effects by correcting the chemical dysregulation that is causing the depression. Two types of medications, [tricyclic antidepressants](https:\/\/www.britannica.com\/science\/tricyclic-antidepressant-drug) and [selective serotonin reuptake inhibitors](https:\/\/www.britannica.com\/science\/selective-serotonin-reuptake-inhibitor) (SSRIs; e.g., fluoxetine \\[[Prozac](https:\/\/www.britannica.com\/science\/Prozac)\\]), though chemically different, both serve to prevent the presynaptic reuptake of serotonin (and in the case of tricyclic antidepressants, norepinephrine as well). This results in the buildup or accumulation of neurotransmitters in the brain and allows them to remain in contact with the [nerve cell](https:\/\/www.britannica.com\/science\/neuron) receptors longer, thus helping to elevate the patient’s mood. By contrast, the antidepressants known as [monoamine oxidase inhibitors](https:\/\/www.britannica.com\/science\/monoamine-oxidase-inhibitor) (MAOIs) interfere with the activity of monoamine oxidase, an [enzyme](https:\/\/www.britannica.com\/science\/enzyme) that is known to be involved in the breakdown of norepinephrine and serotonin.\n\nIn cases of severe depression in which therapeutic results are needed quickly, [electroconvulsive therapy](https:\/\/www.britannica.com\/science\/shock-therapy-psychiatry) (ECT) has sometimes proved helpful. In this procedure, a convulsion is produced by passing an [electric current](https:\/\/www.britannica.com\/science\/electric-current) through the person’s brain. For most persons with depression, however, the best therapeutic results are obtained by using a combination of psychotherapy and [antidepressant](https:\/\/www.britannica.com\/science\/antidepressant) medication. (*See also* [therapeutics](https:\/\/www.britannica.com\/science\/therapeutics\/Psychotherapy#ref22261).)\n\nKey People:\n\n[Viktor Frankl](https:\/\/www.britannica.com\/biography\/Viktor-Frankl)\n\n*(Show more)*\n\nRelated Topics:\n\n[postpartum depression](https:\/\/www.britannica.com\/science\/postpartum-depression)\n\n[persistent depressive disorder](https:\/\/www.britannica.com\/science\/dysthymic-disorder)\n\n[psychotic depression](https:\/\/www.britannica.com\/science\/psychotic-depression)\n\n[Zung Self-Rating Depression Scale](https:\/\/www.britannica.com\/science\/Zung-Self-Rating-Depression-Scale)\n\n[Beck Depression Inventory](https:\/\/www.britannica.com\/science\/Beck-Depression-Inventory)\n\n*(Show more)*\n\n[See all related content](https:\/\/www.britannica.com\/facts\/depression-psychology)\n\nSome persons with depression are affected by treatment-resistant depression (TRD), meaning that they are refractory to existing therapies. For those individuals, scientists have been investigating [alternative](https:\/\/www.merriam-webster.com\/dictionary\/alternative) therapeutic approaches, including [deep brain stimulation](https:\/\/www.britannica.com\/science\/deep-brain-stimulation) (DBS) and [gene therapy](https:\/\/www.britannica.com\/science\/gene-therapy). In DBS, experimental research has focused on the implantation of an electrode in a region of the brain known as the nucleus accumbens, which is located in the striatum (neostriatum) deep within the [cerebral](https:\/\/www.merriam-webster.com\/dictionary\/cerebral) hemispheres and is associated with emotions and feelings such as fear, pleasure, and reward. Studies of depressed animals and postmortem studies of the brains of patients with depression have revealed that reduced levels of a protein known as p11 in cells of the nucleus accumbens are associated with depression. In depressed animals, increasing p11 levels in the nucleus accumbens using gene therapy has been found to relieve depression-like symptoms. Both DBS and gene therapy, however, are associated with potentially dangerous side effects.\n\n[The Editors of Encyclopaedia Britannica](https:\/\/www.britannica.com\/editor\/The-Editors-of-Encyclopaedia-Britannica\/4419)\n\nThis article was most recently revised and updated by [Michael Ray](https:\/\/www.britannica.com\/editor\/Michael-Ray\/6392).\n\n![Britannica AI Icon](https:\/\/cdn.britannica.com\/mendel-resources\/3-178\/images\/chatbot\/star-ai.svg?v=3.178.5)Britannica AI\n\n*chevron\\_right*\n\nDepression\n\n*close*\n\n[AI-generated answers](https:\/\/www.britannica.com\/about-britannica-ai) from Britannica articles. AI makes mistakes, so verify using Britannica articles.\n\nLoad Next Page\n\nFeedback\n\nThank you for your feedback\n\nOur editors will review what you’ve submitted and determine whether to revise the article.\n\n*verified*Cite\n\nWhile every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.\n\nSelect Citation Style\n\nBloom, Floyd E.. \"antidepressant\". *Encyclopedia Britannica*, 21 Mar. 2026, https:\/\/www.britannica.com\/science\/antidepressant. 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Prospects for Genetic Analysis of Drug Mechanisms (PDF)](https:\/\/www.cell.com\/action\/showPdf?pii=S0092-8674%2800%2980042-2)\n- [WebMD - What are the Side Effects of Antidepressants?](https:\/\/www.webmd.com\/depression\/side-effects-antidepressants)\n- [Healthline - What Medications Help Treat Depression?](https:\/\/www.healthline.com\/health\/depression\/medication-list)\n- [MedlinePlus - Antidepressants](https:\/\/medlineplus.gov\/antidepressants.html)\n\nFeedback\n\nThank you for your feedback\n\nOur editors will review what you’ve submitted and determine whether to revise the article.\n\n*print* Print\n\nPlease select which sections you would like to print:\n\n*verified*Cite\n\nWhile every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.\n\nSelect Citation Style\n\nBritannica Editors. \"depression\". *Encyclopedia Britannica*, 1 Mar. 2024, https:\/\/www.britannica.com\/science\/depression-psychology. Accessed 9 April 2026.\n\nCopy Citation\n\nShare\n\nShare to social media\n\n[Facebook](https:\/\/www.facebook.com\/BRITANNICA\/) [X](https:\/\/x.com\/britannica)\n\nURL\n\n<https:\/\/www.britannica.com\/science\/depression-psychology>\n\nExternal Websites\n\n- [World Health Organisation - Depression](https:\/\/www.who.int\/en\/news-room\/fact-sheets\/detail\/depression)\n- [NHS - Clinical Depression](https:\/\/www.nhs.uk\/conditions\/clinical-depression\/)\n- [American Psychiatric Association - Depression](https:\/\/www.psychiatry.org\/patients-families\/depression)\n- [The Nemours Foundation - For Parents - Depression](https:\/\/kidshealth.org\/en\/parents\/understanding-depression.html)\n- [Medicine LibreTexts - Depression](https:\/\/med.libretexts.org\/Courses\/Lumen_Learning\/Book%3A_Wellness_\\(Lumen\\)\/09%3A_Module_5A-_Mental_and_Emotional_Health\/9.04%3A_Depression)\n- [Verywell Mind - Depression](https:\/\/www.verywellmind.com\/depression-4157261)\n- [National Center of Biotechnology Information - Depression](https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK430847\/)\n- [Mayo Clinic - Depression](https:\/\/www.mayoclinic.org\/diseases-conditions\/depression\/symptoms-causes\/syc-20356007)\n- [Cleveland Clinic - Depression](https:\/\/my.clevelandclinic.org\/health\/diseases\/9290-depression)\n- [Natural History Museum - Triceratops](https:\/\/www.nhm.ac.uk\/discover\/dino-directory\/triceratops.html)\n\nBritannica Websites\n\nArticles from Britannica Encyclopedias for elementary and high school students.\n\n- [depression - Student Encyclopedia (Ages 11 and up)](https:\/\/kids.britannica.com\/students\/article\/depression\/341189)","attrs_readable_markdown":"## News •\n**depression**, in [psychology](https:\/\/www.britannica.com\/science\/psychology), a mood or emotional state that is marked by feelings of low self-worth or guilt and a reduced ability to enjoy life. A person who is depressed usually experiences several of the following symptoms: feelings of sadness, hopelessness, or pessimism; lowered [self-esteem](https:\/\/www.britannica.com\/dictionary\/self-esteem) and heightened self-depreciation; a decrease or loss of ability to take pleasure in ordinary activities; reduced energy and vitality; slowness of thought or action; loss of [appetite](https:\/\/www.britannica.com\/science\/appetite); and disturbed [sleep](https:\/\/www.britannica.com\/science\/sleep) or [insomnia](https:\/\/www.britannica.com\/science\/insomnia).\n\nDepression differs from simple grief or mourning, which are appropriate emotional responses to the loss of loved persons or objects. Where there are clear grounds for a person’s unhappiness, depression is considered to be present if the depressed mood is disproportionately long or severe vis-à-vis the precipitating event. The distinctions between the duration of depression, the circumstances under which it arises, and certain other characteristics underlie the classification of depression into different types. Examples of different types of depression include [bipolar disorder](https:\/\/www.britannica.com\/science\/bipolar-disorder), [major depressive disorder](https:\/\/www.britannica.com\/science\/major-depressive-disorder) (clinical depression), [persistent depressive disorder](https:\/\/www.britannica.com\/science\/dysthymic-disorder), and [seasonal affective disorder](https:\/\/www.britannica.com\/science\/seasonal-affective-disorder).\n\n## Characteristics and causes of depression\nDepression is probably the most common psychiatric complaint and has been described by physicians since before the time of ancient Greek physician [Hippocrates](https:\/\/www.britannica.com\/biography\/Hippocrates), who called it [melancholia](https:\/\/www.britannica.com\/science\/melancholia-psychology). The course of the disorder is extremely variable from person to person; it may be mild or severe, [acute](https:\/\/www.merriam-webster.com\/dictionary\/acute) or chronic. Untreated, depression may last an average of four months or longer. Depression is twice as prevalent in women than in men. The typical age of onset is in the 20s, but it may occur at any age.\n\n[![Encyclopaedia Britannica thistle graphic to be used with a Mendel\/Consumer quiz in place of a photograph.](https:\/\/cdn.britannica.com\/05\/215905-131-626D860A\/Encyclopaedia-Britannica-thistle-graphic-logo.jpg) Britannica Quiz 44 Questions from Britannica’s Most Popular Health and Medicine Quizzes](https:\/\/www.britannica.com\/quiz\/44-questions-from-britannicas-most-popular-health-and-medicine-quizzes)\n\nDepression can have many causes. Unfavorable life events can increase a person’s vulnerability to depression or trigger a depressive episode. Negative thoughts about oneself and the world are also important in producing and maintaining depressive symptoms. However, both psychosocial and biochemical mechanisms seem to be important causes; the chief biochemical cause appears to be the defective regulation of the release of one or more naturally occurring [neurotransmitters](https:\/\/www.britannica.com\/science\/neurotransmitter) in the [brain](https:\/\/www.britannica.com\/science\/brain), particularly [norepinephrine](https:\/\/www.britannica.com\/science\/norepinephrine) and [serotonin](https:\/\/www.britannica.com\/science\/serotonin). Reduced quantities or reduced activity of these chemicals in the brain is thought to cause the depressed mood in some sufferers.\n\nDepression is also associated with disordered [rapid eye movement (REM) sleep](https:\/\/www.britannica.com\/science\/rapid-eye-movement-sleep). A region of the brain known as the [amygdala](https:\/\/www.britannica.com\/science\/amygdala) contains [neurons](https:\/\/www.britannica.com\/science\/neuron) that project into the [brainstem](https:\/\/www.britannica.com\/science\/brainstem) and appear to be involved in modulating REM sleep. The amygdala is also associated with processing negative thoughts and may be enlarged, hyperactive, or otherwise dysfunctional in some depressed persons. Although the significance of these associations is [yet](https:\/\/www.britannica.com\/dictionary\/yet) to be defined, the link between depression, disordered REM sleep, and abnormalities of the amygdala has led to new avenues of research into the neurobiology and treatment of depression.\n\nResearch suggests that depression is also linked to [physical activity](https:\/\/www.britannica.com\/topic\/physical-activity), whereby physical activity may lower a person’s risk of developing depression. Individuals who [exercise](https:\/\/www.britannica.com\/topic\/exercise-physical-fitness) typically report better [mental health](https:\/\/www.britannica.com\/science\/mental-hygiene) and are less likely to be depressed, compared with individuals who do not exercise.\n\n## Types of depression\n[Bipolar disorder](https:\/\/www.britannica.com\/science\/bipolar-disorder), major depressive disorder, and persistent depressive disorder are the primary types of depression. A person who experiences alternating states of depression and [mania](https:\/\/www.britannica.com\/science\/mania) (abnormal elevation of mood) or hypomania (distinct, though not necessarily abnormal, elevation of mood) is said to suffer from bipolar disorder. [Major depressive disorder](https:\/\/www.britannica.com\/science\/major-depressive-disorder) is [characterized](https:\/\/www.britannica.com\/dictionary\/characterized) by severe symptoms that disrupt the individual’s daily life, typically with effects on appetite, sleep, work, or the ability to enjoy life. Episodes of major depression can occur at any age and may occur once or multiple times in an affected person’s life. [Persistent depressive disorder](https:\/\/www.britannica.com\/science\/dysthymic-disorder) involves symptoms that last two or more years, sometimes marked by episodes of major depression.\n\nSmart, reliable knowledge for professionals, students, and curious minds everywhere.\n\n[SUBSCRIBE](https:\/\/premium.britannica.com\/premium-membership\/?utm_source=premium&utm_medium=inline-cta&utm_campaign=smart-2026)\n\n![Penguin, ship, mountain, atlas](https:\/\/cdn.britannica.com\/marketing\/inline-left.webp)\n\n![shohei ohtani, plants, andy wharhol art](https:\/\/cdn.britannica.com\/marketing\/inline-right.webp)\n\n![Mobile](https:\/\/cdn.britannica.com\/marketing\/inline-mobile.webp?w=400)\n\nOther types of depression include postpartum depression, psychotic depression, and seasonal affective disorder, each of which develops under specific circumstances. [Postpartum depression](https:\/\/www.britannica.com\/science\/postpartum-depression) develops in women in the period following [childbirth](https:\/\/www.britannica.com\/science\/birth). Symptoms include [anxiety](https:\/\/www.britannica.com\/science\/anxiety), a lack of interest in caring for the infant, and feelings of sadness, hopelessness, or inadequacy. Postpartum depression is longer-lasting and more severe than the “baby blues,” a common condition among women after childbirth that typically involves mood swings, feelings of sadness, and crying spells. Psychotic depression arises against a background of [psychosis](https:\/\/www.britannica.com\/science\/psychosis), which may involve symptoms of [delusions](https:\/\/www.merriam-webster.com\/dictionary\/delusions), hallucinations, or [paranoia](https:\/\/www.britannica.com\/science\/paranoia). [Seasonal affective disorder](https:\/\/www.britannica.com\/science\/seasonal-affective-disorder) is characterized by the onset of depressive symptoms in autumn and winter, which are [alleviated](https:\/\/www.merriam-webster.com\/dictionary\/alleviated) with increased exposure to natural light in spring and summer.\n\n## Treatments for depression\nThere are three main treatments for depression. The two most important—and widespread by far—are [psychotherapy](https:\/\/www.britannica.com\/science\/psychotherapy) and psychotropic [medication](https:\/\/www.britannica.com\/science\/drug-chemical-agent), specifically [antidepressants](https:\/\/www.britannica.com\/science\/antidepressant) such as [bupropion](https:\/\/www.britannica.com\/science\/bupropion). Psychotherapy aims to alter the patient’s maladaptive [cognitive](https:\/\/www.merriam-webster.com\/dictionary\/cognitive) and behavioral responses to stressful life events while also giving emotional support to the patient. Antidepressant medications, by contrast, directly affect the chemistry of the brain and presumably achieve their therapeutic effects by correcting the chemical dysregulation that is causing the depression. Two types of medications, [tricyclic antidepressants](https:\/\/www.britannica.com\/science\/tricyclic-antidepressant-drug) and [selective serotonin reuptake inhibitors](https:\/\/www.britannica.com\/science\/selective-serotonin-reuptake-inhibitor) (SSRIs; e.g., fluoxetine \\[[Prozac](https:\/\/www.britannica.com\/science\/Prozac)\\]), though chemically different, both serve to prevent the presynaptic reuptake of serotonin (and in the case of tricyclic antidepressants, norepinephrine as well). This results in the buildup or accumulation of neurotransmitters in the brain and allows them to remain in contact with the [nerve cell](https:\/\/www.britannica.com\/science\/neuron) receptors longer, thus helping to elevate the patient’s mood. By contrast, the antidepressants known as [monoamine oxidase inhibitors](https:\/\/www.britannica.com\/science\/monoamine-oxidase-inhibitor) (MAOIs) interfere with the activity of monoamine oxidase, an [enzyme](https:\/\/www.britannica.com\/science\/enzyme) that is known to be involved in the breakdown of norepinephrine and serotonin.\n\nIn cases of severe depression in which therapeutic results are needed quickly, [electroconvulsive therapy](https:\/\/www.britannica.com\/science\/shock-therapy-psychiatry) (ECT) has sometimes proved helpful. In this procedure, a convulsion is produced by passing an [electric current](https:\/\/www.britannica.com\/science\/electric-current) through the person’s brain. For most persons with depression, however, the best therapeutic results are obtained by using a combination of psychotherapy and [antidepressant](https:\/\/www.britannica.com\/science\/antidepressant) medication. (*See also* [therapeutics](https:\/\/www.britannica.com\/science\/therapeutics\/Psychotherapy#ref22261).)\n\nSome persons with depression are affected by treatment-resistant depression (TRD), meaning that they are refractory to existing therapies. For those individuals, scientists have been investigating [alternative](https:\/\/www.merriam-webster.com\/dictionary\/alternative) therapeutic approaches, including [deep brain stimulation](https:\/\/www.britannica.com\/science\/deep-brain-stimulation) (DBS) and [gene therapy](https:\/\/www.britannica.com\/science\/gene-therapy). In DBS, experimental research has focused on the implantation of an electrode in a region of the brain known as the nucleus accumbens, which is located in the striatum (neostriatum) deep within the [cerebral](https:\/\/www.merriam-webster.com\/dictionary\/cerebral) hemispheres and is associated with emotions and feelings such as fear, pleasure, and reward. Studies of depressed animals and postmortem studies of the brains of patients with depression have revealed that reduced levels of a protein known as p11 in cells of the nucleus accumbens are associated with depression. In depressed animals, increasing p11 levels in the nucleus accumbens using gene therapy has been found to relieve depression-like symptoms. Both DBS and gene therapy, however, are associated with potentially dangerous side effects.\n\nThis article was most recently revised and updated by [Michael Ray](https:\/\/www.britannica.com\/editor\/Michael-Ray\/6392).","meta_canonical":null}

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Meta Description	Antidepressant, any member of a class of drugs prescribed to relieve depression. There are several major classes of antidepressant drugs, the best known of which include the tricyclic antidepressants, monoamine oxidase inhibitors (MAOIs), and selective serotonin reuptake inhibitors (SSRIs). Other
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Boilerpipe Text	News • depression , in psychology , a mood or emotional state that is marked by feelings of low self-worth or guilt and a reduced ability to enjoy life. A person who is depressed usually experiences several of the following symptoms: feelings of sadness, hopelessness, or pessimism; lowered self-esteem and heightened self-depreciation; a decrease or loss of ability to take pleasure in ordinary activities; reduced energy and vitality; slowness of thought or action; loss of appetite ; and disturbed sleep or insomnia . Depression differs from simple grief or mourning, which are appropriate emotional responses to the loss of loved persons or objects. Where there are clear grounds for a person’s unhappiness, depression is considered to be present if the depressed mood is disproportionately long or severe vis-à-vis the precipitating event. The distinctions between the duration of depression, the circumstances under which it arises, and certain other characteristics underlie the classification of depression into different types. Examples of different types of depression include bipolar disorder , major depressive disorder (clinical depression), persistent depressive disorder , and seasonal affective disorder . Characteristics and causes of depression Depression is probably the most common psychiatric complaint and has been described by physicians since before the time of ancient Greek physician Hippocrates , who called it melancholia . The course of the disorder is extremely variable from person to person; it may be mild or severe, acute or chronic. Untreated, depression may last an average of four months or longer. Depression is twice as prevalent in women than in men. The typical age of onset is in the 20s, but it may occur at any age. Britannica Quiz 44 Questions from Britannica’s Most Popular Health and Medicine Quizzes Depression can have many causes. Unfavorable life events can increase a person’s vulnerability to depression or trigger a depressive episode. Negative thoughts about oneself and the world are also important in producing and maintaining depressive symptoms. However, both psychosocial and biochemical mechanisms seem to be important causes; the chief biochemical cause appears to be the defective regulation of the release of one or more naturally occurring neurotransmitters in the brain , particularly norepinephrine and serotonin . Reduced quantities or reduced activity of these chemicals in the brain is thought to cause the depressed mood in some sufferers. Depression is also associated with disordered rapid eye movement (REM) sleep . A region of the brain known as the amygdala contains neurons that project into the brainstem and appear to be involved in modulating REM sleep. The amygdala is also associated with processing negative thoughts and may be enlarged, hyperactive, or otherwise dysfunctional in some depressed persons. Although the significance of these associations is yet to be defined, the link between depression, disordered REM sleep, and abnormalities of the amygdala has led to new avenues of research into the neurobiology and treatment of depression. Research suggests that depression is also linked to physical activity , whereby physical activity may lower a person’s risk of developing depression. Individuals who exercise typically report better mental health and are less likely to be depressed, compared with individuals who do not exercise. Types of depression Bipolar disorder , major depressive disorder, and persistent depressive disorder are the primary types of depression. A person who experiences alternating states of depression and mania (abnormal elevation of mood) or hypomania (distinct, though not necessarily abnormal, elevation of mood) is said to suffer from bipolar disorder. Major depressive disorder is characterized by severe symptoms that disrupt the individual’s daily life, typically with effects on appetite, sleep, work, or the ability to enjoy life. Episodes of major depression can occur at any age and may occur once or multiple times in an affected person’s life. Persistent depressive disorder involves symptoms that last two or more years, sometimes marked by episodes of major depression. Smart, reliable knowledge for professionals, students, and curious minds everywhere. SUBSCRIBE Other types of depression include postpartum depression, psychotic depression, and seasonal affective disorder, each of which develops under specific circumstances. Postpartum depression develops in women in the period following childbirth . Symptoms include anxiety , a lack of interest in caring for the infant, and feelings of sadness, hopelessness, or inadequacy. Postpartum depression is longer-lasting and more severe than the “baby blues,” a common condition among women after childbirth that typically involves mood swings, feelings of sadness, and crying spells. Psychotic depression arises against a background of psychosis , which may involve symptoms of delusions , hallucinations, or paranoia . Seasonal affective disorder is characterized by the onset of depressive symptoms in autumn and winter, which are alleviated with increased exposure to natural light in spring and summer. Treatments for depression There are three main treatments for depression. The two most important—and widespread by far—are psychotherapy and psychotropic medication , specifically antidepressants such as bupropion . Psychotherapy aims to alter the patient’s maladaptive cognitive and behavioral responses to stressful life events while also giving emotional support to the patient. Antidepressant medications, by contrast, directly affect the chemistry of the brain and presumably achieve their therapeutic effects by correcting the chemical dysregulation that is causing the depression. Two types of medications, tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs; e.g., fluoxetine [ Prozac ]), though chemically different, both serve to prevent the presynaptic reuptake of serotonin (and in the case of tricyclic antidepressants, norepinephrine as well). This results in the buildup or accumulation of neurotransmitters in the brain and allows them to remain in contact with the nerve cell receptors longer, thus helping to elevate the patient’s mood. By contrast, the antidepressants known as monoamine oxidase inhibitors (MAOIs) interfere with the activity of monoamine oxidase, an enzyme that is known to be involved in the breakdown of norepinephrine and serotonin. In cases of severe depression in which therapeutic results are needed quickly, electroconvulsive therapy (ECT) has sometimes proved helpful. In this procedure, a convulsion is produced by passing an electric current through the person’s brain. For most persons with depression, however, the best therapeutic results are obtained by using a combination of psychotherapy and antidepressant medication. ( See also therapeutics .) Some persons with depression are affected by treatment-resistant depression (TRD), meaning that they are refractory to existing therapies. For those individuals, scientists have been investigating alternative therapeutic approaches, including deep brain stimulation (DBS) and gene therapy . In DBS, experimental research has focused on the implantation of an electrode in a region of the brain known as the nucleus accumbens, which is located in the striatum (neostriatum) deep within the cerebral hemispheres and is associated with emotions and feelings such as fear, pleasure, and reward. Studies of depressed animals and postmortem studies of the brains of patients with depression have revealed that reduced levels of a protein known as p11 in cells of the nucleus accumbens are associated with depression. In depressed animals, increasing p11 levels in the nucleus accumbens using gene therapy has been found to relieve depression-like symptoms. Both DBS and gene therapy, however, are associated with potentially dangerous side effects. This article was most recently revised and updated by Michael Ray .
Markdown	[![Encyclopedia Britannica](https://cdn.britannica.com/mendel/eb-logo/MendelNewThistleLogo.png)](https://www.britannica.com/) [![Encyclopedia Britannica](https://cdn.britannica.com/mendel/eb-logo/MendelNewThistleLogo.png)](https://www.britannica.com/) [SUBSCRIBE](https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=global-nav&utm_campaign=blue-evergreen) [SUBSCRIBE](https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=global-nav-mobile&utm_campaign=blue-evergreen) Login https://premium.britannica.com/premium-membership/?utm\_source=premium\&utm\_medium=nav-login-box\&utm\_campaign=evergreen [SUBSCRIBE](https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=hamburger-menu&utm_campaign=blue) [Ask the Chatbot](https://www.britannica.com/chatbot) [Games & Quizzes](https://www.britannica.com/quiz/browse) [History & Society](https://www.britannica.com/History-Society) [Science & Tech](https://www.britannica.com/Science-Tech) [Biographies](https://www.britannica.com/Biographies) [Animals & Nature](https://www.britannica.com/Animals-Nature) [Geography & Travel](https://www.britannica.com/Geography-Travel) [Arts & Culture](https://www.britannica.com/Arts-Culture) [ProCon](https://www.britannica.com/procon) [Money](https://www.britannica.com/money) [Videos](https://www.britannica.com/videos) [antidepressant](https://www.britannica.com/science/antidepressant) [Introduction](https://www.britannica.com/science/antidepressant) [References & Edit History](https://www.britannica.com/science/antidepressant/additional-info) [Quick Facts & Related Topics](https://www.britannica.com/facts/antidepressant) [Images](https://www.britannica.com/science/antidepressant/images-videos) [![Prozac](https://cdn.britannica.com/50/123550-004-4E7CBC62/Prozac-pills.jpg)](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg) At a Glance [![Prozac](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg?w=200&h=200&c=crop)](https://www.britannica.com/summary/antidepressant) [antidepressant summary](https://www.britannica.com/summary/antidepressant) ![Britannica AI Icon](https://cdn.britannica.com/mendel-resources/3-178/images/chatbot/star-ai.svg?v=3.178.5) Contents Ask Anything [Health & Medicine](https://www.britannica.com/browse/Health-Medicine) [Medicine](https://www.britannica.com/browse/Medicine) CITE Share Feedback External Websites [![Prozac](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg?w=400&h=300&c=crop)](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg) [Prozac](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg) Prozac pills. (more) # antidepressant Homework Help Also known as: antidepressant drug, psychic energizer Written by [Floyd E. Bloom Chairman, Department of Neuropharmacology, Scripps Research Institute, La Jolla, California. Editor in Chief, Science magazine. Coauthor of Biochemical Basis of Neuropharmacology and...](https://www.britannica.com/contributor/Floyd-E-Bloom/307) Floyd E. Bloom Fact-checked by [Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....](https://www.britannica.com/editor/The-Editors-of-Encyclopaedia-Britannica/4419) Britannica Editors Last updated Mar. 21, 2026 •[History](https://www.britannica.com/science/antidepressant/additional-info#history) ![Britannica AI Icon](https://cdn.britannica.com/mendel-resources/3-178/images/chatbot/star-ai.svg?v=3.178.5) Britannica AI Ask Anything Table of Contents Table of Contents Ask Anything ## News • [No evidence for psychedelics and depression despite 'hype'](https://www.abc.net.au/news/science/2026-03-19/psychedlics-may-be-no-better-than-antidepressants-for-depression/106467464) • Mar. 18, 2026, 1:30 PM ET (ABC News (Australia)) Show less Top Questions - What is an antidepressant? - Why are antidepressants used? - How do antidepressants help with depression? - Are there different types of antidepressants? - What are some possible side effects of antidepressants? - How do doctors decide which antidepressant is best for a patient? Show more Show less antidepressant, any member of a class of [drugs](https://www.britannica.com/science/drug-chemical-agent) prescribed to relieve [depression](https://www.britannica.com/science/depression-psychology). There are several major classes of antidepressant drugs, the best known of which include the tricyclic antidepressants, [monoamine oxidase inhibitor](https://www.britannica.com/science/monoamine-oxidase-inhibitor)s (MAOIs), and selective [serotonin](https://www.britannica.com/science/serotonin) reuptake inhibitors ([SSRI](https://www.britannica.com/science/selective-serotonin-reuptake-inhibitor)s). Other important groups include the [norepinephrine](https://www.britannica.com/science/epinephrine) reuptake inhibitors (NRIs), the serotonin-norepinephrine reuptake inhibitors (SNRIs), and the [atypical](https://www.merriam-webster.com/dictionary/atypical) antidepressants, a [disparate](https://www.merriam-webster.com/dictionary/disparate) group of agents that possess unique structural features and mechanisms of action. Chemically speaking, depression is apparently caused by reduced quantities or reduced activity of the monoamine [neurotransmitters](https://www.britannica.com/science/neurotransmitter) (e.g., serotonin, norepinephrine, and [dopamine](https://www.britannica.com/science/dopamine)) within the [brain](https://www.britannica.com/science/brain). This [etiology](https://www.merriam-webster.com/dictionary/etiology) is supported by evidence that drugs that restore chemical imbalances in the levels of neurotransmitters in the brain effectively [mitigate](https://www.merriam-webster.com/dictionary/mitigate) symptoms of depression. All antidepressants, in fact, achieve their effects by [inhibiting](https://www.merriam-webster.com/dictionary/inhibiting) the body’s reabsorption or inactivation of monoamine neurotransmitters, thus allowing the neurotransmitters to accumulate and remain in contact with their [receptors](https://www.britannica.com/science/receptor-nerve-ending) for prolonged periods of time; these changes seem to be important in elevating mood and relieving depression. One of the first antidepressants to demonstrate success clinically was [iproniazid](https://www.britannica.com/science/iproniazid), a [drug](https://www.britannica.com/science/drug-chemical-agent) developed originally for the [treatment](https://www.britannica.com/science/therapeutics) of [tuberculosis](https://www.britannica.com/science/tuberculosis). In the 1950s scientists discovered that the extreme euphoria and hyperactivity experienced by some patients who were taking iproniazid was caused by the drug’s inhibition of monoamine oxidase, an [enzyme](https://www.britannica.com/science/enzyme) in the [liver](https://www.britannica.com/science/liver) and brain that normally breaks down the monoamine neurotransmitters. Drugs that were better at blocking the activity of this enzyme were even more effective in evoking euphoria. As a group, these drugs came to be known as MAOIs. [![Prozac](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg) More From Britannica therapeutics: Antidepressant drugs](https://www.britannica.com/science/therapeutics/Psychotherapy#ref294028) Also in the 1950s the first [tricyclic antidepressants](https://www.britannica.com/science/tricyclic-antidepressant-drug) were discovered. These agents, so called because they are composed chemically of three [carbon](https://www.britannica.com/science/carbon-chemical-element) rings, [inhibit](https://www.merriam-webster.com/dictionary/inhibit) the active reuptake, to varying degrees, of norepinephrine, serotonin, and dopamine in the brain. The tricyclics include [imipramine](https://www.britannica.com/science/imipramine), [amitriptyline](https://www.britannica.com/science/amitriptyline), [desipramine](https://www.britannica.com/science/desmethylimipramine), nortriptyline, and a number of other [compounds](https://www.merriam-webster.com/dictionary/compounds). These drugs relieve symptoms in a high proportion (more than 70 percent) of depressed patients. As with the MAOIs, the antidepressant action of tricyclic drugs may not become apparent until two to four weeks after treatment begins. [SSRI](https://www.britannica.com/science/selective-serotonin-reuptake-inhibitor)s were introduced in the 1980s, and shortly thereafter they became some of the most commonly used antidepressants, primarily because they have fewer side effects than [tricyclic](https://www.britannica.com/science/tricyclic-antidepressant-drug)s or MAOIs. SSRIs include fluoxetine ([Prozac](https://www.britannica.com/science/Prozac)), paroxetine (Paxil), and sertraline (Zoloft). SSRIs are also used in the treatment of [anxiety](https://www.britannica.com/science/anxiety), [eating disorders](https://www.britannica.com/science/eating-disorder), [panic disorder](https://www.britannica.com/science/panic-disorder), [obsessive-compulsive disorder](https://www.britannica.com/science/obsessive-compulsive-disorder), and [borderline personality disorder](https://www.britannica.com/science/borderline-personality-disorder). Other antidepressants inhibit the reuptake of monoamine neurotransmitters in variable amounts. For example, the SNRI venlafaxine blocks both serotonin and norepinephrine reuptake; therapeutic doses of the drug, however, also weakly inhibit dopamine reuptake. Nefazodone, an atypical antidepressant, [inhibits](https://www.merriam-webster.com/dictionary/inhibits) serotonin and norepinephrine reuptake and is an [antagonist](https://www.merriam-webster.com/dictionary/antagonist) at certain serotonin receptors and at α1\-adrenoceptors. Three to four weeks are typically required to produce significant improvement in individuals who are taking antidepressant medications. Most physicians recommend that patients continue to take antidepressants for at least six months to prevent a relapse. The type of antidepressant that a physician prescribes depends largely on symptoms and severity of the condition and on the patient’s tolerance of side effects. For instance, the MAOIs—chiefly isocarboxazid, phenelzine, and tranylcypromine—in general are used only after treatment with tricyclic drugs has proved unsatisfactory, because these drugs’ side effects are unpredictable and their complex interactions are incompletely understood. Fluoxetine often relieves cases of depression that have failed to yield to tricyclics or MAOIs. Related Topics: [bupropion](https://www.britannica.com/science/bupropion) [trazodone](https://www.britannica.com/topic/trazodone) [tricyclic antidepressant drug](https://www.britannica.com/science/tricyclic-antidepressant-drug) [selective serotonin reuptake inhibitor](https://www.britannica.com/science/selective-serotonin-reuptake-inhibitor) [monoamine oxidase inhibitor](https://www.britannica.com/science/monoamine-oxidase-inhibitor) (Show more) [See all related content](https://www.britannica.com/facts/antidepressant) Explore Britannica Premium\! Go beyond the basics with trusted, in-depth knowledge for professionals, students, and lifelong learners. [SUBSCRIBE](https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=inline-cta&utm_campaign=basics-2026) ![Penguin, ship, mountain, atlas](https://cdn.britannica.com/marketing/inline-left.webp) ![shohei ohtani, plants, andy wharhol art](https://cdn.britannica.com/marketing/inline-right.webp) ![Mobile](https://cdn.britannica.com/marketing/inline-mobile.webp?w=400) Side effects vary among the types of antidepressants and may include sleepiness, tremors, [anxiety](https://www.britannica.com/science/anxiety), loss of sexual desire, and [nausea](https://www.britannica.com/science/nausea-pathology). The possible side effects of tricyclics specifically include dry mouth, blurred [vision](https://www.britannica.com/science/vision-physiology), [constipation](https://www.britannica.com/science/constipation), dizziness, and difficulty in [urination](https://www.britannica.com/science/urination). [Cerebral](https://www.merriam-webster.com/dictionary/Cerebral) and cardiac toxicity have been observed in some individuals. In rare instances, antidepressants may cause life-threatening side effects. For instance, nefazodone is associated with a low risk of death from hepatic (liver) failure; the discovery of this risk association resulted in the drug’s discontinuation in the [United States](https://www.britannica.com/place/United-States). Many antidepressants also have the potential to produce dangerous drug interactions. This is especially true of MAOIs; the interaction of these drugs with tyramine, which is found in many foods as well as in [wine](https://www.britannica.com/topic/wine) and certain types of [beer](https://www.britannica.com/topic/beer), can cause [hypertension](https://www.britannica.com/science/hypertension) (high [blood pressure](https://www.britannica.com/science/blood-pressure)) and severe [headache](https://www.britannica.com/science/headache). [Floyd E. Bloom](https://www.britannica.com/contributor/Floyd-E-Bloom/307) [The Editors of Encyclopaedia Britannica](https://www.britannica.com/editor/The-Editors-of-Encyclopaedia-Britannica/4419) ![Britannica AI Icon](https://cdn.britannica.com/mendel-resources/3-178/images/chatbot/star-ai.svg?v=3.178.5)Britannica AI chevron\_right Antidepressant close [AI-generated answers](https://www.britannica.com/about-britannica-ai) from Britannica articles. AI makes mistakes, so verify using Britannica articles. [depression](https://www.britannica.com/science/depression-psychology) - [Introduction](https://www.britannica.com/science/depression-psychology) - [Characteristics and causes of depression](https://www.britannica.com/science/depression-psychology#ref297878) - [Types of depression](https://www.britannica.com/science/depression-psychology#ref321576) - [Treatments for depression](https://www.britannica.com/science/depression-psychology#ref297879) [References & Edit History](https://www.britannica.com/science/depression-psychology/additional-info) [Quick Facts & Related Topics](https://www.britannica.com/facts/depression-psychology) [Images & Videos](https://www.britannica.com/science/depression-psychology/images-videos) [![Prozac](https://cdn.britannica.com/50/123550-004-4E7CBC62/Prozac-pills.jpg)](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg) [![Understanding seasonal affective disorder](https://cdn.britannica.com/18/188818-138-057CE8AE/chemistry-seasonal-affective-disorder.jpg?w=400&h=225&c=crop)](https://www.britannica.com/video/chemistry-seasonal-affective-disorder/-208059) At a Glance [![default image](https://cdn.britannica.com/mendel-resources/3-178/images/shared/new-thistle.svg?v=3.178.5)](https://www.britannica.com/summary/depression-psychology) [depression summary](https://www.britannica.com/summary/depression-psychology) Quizzes [![Encyclopaedia Britannica thistle graphic to be used with a Mendel/Consumer quiz in place of a photograph.](https://cdn.britannica.com/05/215905-131-626D860A/Encyclopaedia-Britannica-thistle-graphic-logo.jpg?w=200&h=200&c=crop)](https://www.britannica.com/quiz/44-questions-from-britannicas-most-popular-health-and-medicine-quizzes) [44 Questions from Britannica’s Most Popular Health and Medicine Quizzes](https://www.britannica.com/quiz/44-questions-from-britannicas-most-popular-health-and-medicine-quizzes) ![Britannica AI Icon](https://cdn.britannica.com/mendel-resources/3-178/images/chatbot/star-ai.svg?v=3.178.5) Ask Anything Quick Summary [Health & Medicine](https://www.britannica.com/browse/Health-Medicine) [Conditions & Diseases](https://www.britannica.com/browse/Conditions-Diseases) [Mental Disorders](https://www.britannica.com/browse/Mental-Disorders) CITE Share Feedback External Websites [![Prozac](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg?w=400&h=300&c=crop)](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg) [Prozac](https://cdn.britannica.com/50/123550-050-885369B3/Prozac-pills.jpg) Prozac pills. (more) # depression psychology Homework Help Also known as: mental depression Written and fact-checked by [Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....](https://www.britannica.com/editor/The-Editors-of-Encyclopaedia-Britannica/4419) Britannica Editors [History](https://www.britannica.com/science/depression-psychology/additional-info#history) ![Britannica AI Icon](https://cdn.britannica.com/mendel-resources/3-178/images/chatbot/star-ai.svg?v=3.178.5) Britannica AI Ask Anything Quick Summary Table of Contents Table of Contents Quick Summary Ask Anything ## News • [Fathers face rising depression risk a year after baby arrives](https://www.sciencedaily.com/releases/2026/03/260324230057.htm) • Mar. 24, 2026, 11:10 PM ET (ScienceDaily) ...(Show more) [No evidence for psychedelics and depression despite 'hype'](https://www.abc.net.au/news/science/2026-03-19/psychedlics-may-be-no-better-than-antidepressants-for-depression/106467464) • Mar. 18, 2026, 1:30 PM ET (ABC News (Australia)) Show less depression, in [psychology](https://www.britannica.com/science/psychology), a mood or emotional state that is marked by feelings of low self-worth or guilt and a reduced ability to enjoy life. A person who is depressed usually experiences several of the following symptoms: feelings of sadness, hopelessness, or pessimism; lowered [self-esteem](https://www.britannica.com/dictionary/self-esteem) and heightened self-depreciation; a decrease or loss of ability to take pleasure in ordinary activities; reduced energy and vitality; slowness of thought or action; loss of [appetite](https://www.britannica.com/science/appetite); and disturbed [sleep](https://www.britannica.com/science/sleep) or [insomnia](https://www.britannica.com/science/insomnia). If you are experiencing a crisis or would like to speak with someone about depression, call the [National Suicide and Crisis Lifeline](https://988lifeline.org/) at 988 or contact the [Crisis Text Line](https://www.crisistextline.org/) by texting HOME to 741741. Depression differs from simple grief or mourning, which are appropriate emotional responses to the loss of loved persons or objects. Where there are clear grounds for a person’s unhappiness, depression is considered to be present if the depressed mood is disproportionately long or severe vis-à-vis the precipitating event. The distinctions between the duration of depression, the circumstances under which it arises, and certain other characteristics underlie the classification of depression into different types. Examples of different types of depression include [bipolar disorder](https://www.britannica.com/science/bipolar-disorder), [major depressive disorder](https://www.britannica.com/science/major-depressive-disorder) (clinical depression), [persistent depressive disorder](https://www.britannica.com/science/dysthymic-disorder), and [seasonal affective disorder](https://www.britannica.com/science/seasonal-affective-disorder). ## Characteristics and causes of depression Depression is probably the most common psychiatric complaint and has been described by physicians since before the time of ancient Greek physician [Hippocrates](https://www.britannica.com/biography/Hippocrates), who called it [melancholia](https://www.britannica.com/science/melancholia-psychology). The course of the disorder is extremely variable from person to person; it may be mild or severe, [acute](https://www.merriam-webster.com/dictionary/acute) or chronic. Untreated, depression may last an average of four months or longer. Depression is twice as prevalent in women than in men. The typical age of onset is in the 20s, but it may occur at any age. [![Encyclopaedia Britannica thistle graphic to be used with a Mendel/Consumer quiz in place of a photograph.](https://cdn.britannica.com/05/215905-131-626D860A/Encyclopaedia-Britannica-thistle-graphic-logo.jpg) Britannica Quiz 44 Questions from Britannica’s Most Popular Health and Medicine Quizzes](https://www.britannica.com/quiz/44-questions-from-britannicas-most-popular-health-and-medicine-quizzes) Depression can have many causes. Unfavorable life events can increase a person’s vulnerability to depression or trigger a depressive episode. Negative thoughts about oneself and the world are also important in producing and maintaining depressive symptoms. However, both psychosocial and biochemical mechanisms seem to be important causes; the chief biochemical cause appears to be the defective regulation of the release of one or more naturally occurring [neurotransmitters](https://www.britannica.com/science/neurotransmitter) in the [brain](https://www.britannica.com/science/brain), particularly [norepinephrine](https://www.britannica.com/science/norepinephrine) and [serotonin](https://www.britannica.com/science/serotonin). Reduced quantities or reduced activity of these chemicals in the brain is thought to cause the depressed mood in some sufferers. Depression is also associated with disordered [rapid eye movement (REM) sleep](https://www.britannica.com/science/rapid-eye-movement-sleep). A region of the brain known as the [amygdala](https://www.britannica.com/science/amygdala) contains [neurons](https://www.britannica.com/science/neuron) that project into the [brainstem](https://www.britannica.com/science/brainstem) and appear to be involved in modulating REM sleep. The amygdala is also associated with processing negative thoughts and may be enlarged, hyperactive, or otherwise dysfunctional in some depressed persons. Although the significance of these associations is [yet](https://www.britannica.com/dictionary/yet) to be defined, the link between depression, disordered REM sleep, and abnormalities of the amygdala has led to new avenues of research into the neurobiology and treatment of depression. Research suggests that depression is also linked to [physical activity](https://www.britannica.com/topic/physical-activity), whereby physical activity may lower a person’s risk of developing depression. Individuals who [exercise](https://www.britannica.com/topic/exercise-physical-fitness) typically report better [mental health](https://www.britannica.com/science/mental-hygiene) and are less likely to be depressed, compared with individuals who do not exercise. ## Types of depression [Bipolar disorder](https://www.britannica.com/science/bipolar-disorder), major depressive disorder, and persistent depressive disorder are the primary types of depression. A person who experiences alternating states of depression and [mania](https://www.britannica.com/science/mania) (abnormal elevation of mood) or hypomania (distinct, though not necessarily abnormal, elevation of mood) is said to suffer from bipolar disorder. [Major depressive disorder](https://www.britannica.com/science/major-depressive-disorder) is [characterized](https://www.britannica.com/dictionary/characterized) by severe symptoms that disrupt the individual’s daily life, typically with effects on appetite, sleep, work, or the ability to enjoy life. Episodes of major depression can occur at any age and may occur once or multiple times in an affected person’s life. [Persistent depressive disorder](https://www.britannica.com/science/dysthymic-disorder) involves symptoms that last two or more years, sometimes marked by episodes of major depression. Explore Britannica Premium\! Smart, reliable knowledge for professionals, students, and curious minds everywhere. [SUBSCRIBE](https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=inline-cta&utm_campaign=smart-2026) ![Penguin, ship, mountain, atlas](https://cdn.britannica.com/marketing/inline-left.webp) ![shohei ohtani, plants, andy wharhol art](https://cdn.britannica.com/marketing/inline-right.webp) ![Mobile](https://cdn.britannica.com/marketing/inline-mobile.webp?w=400) Other types of depression include postpartum depression, psychotic depression, and seasonal affective disorder, each of which develops under specific circumstances. [Postpartum depression](https://www.britannica.com/science/postpartum-depression) develops in women in the period following [childbirth](https://www.britannica.com/science/birth). Symptoms include [anxiety](https://www.britannica.com/science/anxiety), a lack of interest in caring for the infant, and feelings of sadness, hopelessness, or inadequacy. Postpartum depression is longer-lasting and more severe than the “baby blues,” a common condition among women after childbirth that typically involves mood swings, feelings of sadness, and crying spells. Psychotic depression arises against a background of [psychosis](https://www.britannica.com/science/psychosis), which may involve symptoms of [delusions](https://www.merriam-webster.com/dictionary/delusions), hallucinations, or [paranoia](https://www.britannica.com/science/paranoia). [Seasonal affective disorder](https://www.britannica.com/science/seasonal-affective-disorder) is characterized by the onset of depressive symptoms in autumn and winter, which are [alleviated](https://www.merriam-webster.com/dictionary/alleviated) with increased exposure to natural light in spring and summer. ## Treatments for depression There are three main treatments for depression. The two most important—and widespread by far—are [psychotherapy](https://www.britannica.com/science/psychotherapy) and psychotropic [medication](https://www.britannica.com/science/drug-chemical-agent), specifically [antidepressants](https://www.britannica.com/science/antidepressant) such as [bupropion](https://www.britannica.com/science/bupropion). Psychotherapy aims to alter the patient’s maladaptive [cognitive](https://www.merriam-webster.com/dictionary/cognitive) and behavioral responses to stressful life events while also giving emotional support to the patient. Antidepressant medications, by contrast, directly affect the chemistry of the brain and presumably achieve their therapeutic effects by correcting the chemical dysregulation that is causing the depression. Two types of medications, [tricyclic antidepressants](https://www.britannica.com/science/tricyclic-antidepressant-drug) and [selective serotonin reuptake inhibitors](https://www.britannica.com/science/selective-serotonin-reuptake-inhibitor) (SSRIs; e.g., fluoxetine \[[Prozac](https://www.britannica.com/science/Prozac)\]), though chemically different, both serve to prevent the presynaptic reuptake of serotonin (and in the case of tricyclic antidepressants, norepinephrine as well). This results in the buildup or accumulation of neurotransmitters in the brain and allows them to remain in contact with the [nerve cell](https://www.britannica.com/science/neuron) receptors longer, thus helping to elevate the patient’s mood. By contrast, the antidepressants known as [monoamine oxidase inhibitors](https://www.britannica.com/science/monoamine-oxidase-inhibitor) (MAOIs) interfere with the activity of monoamine oxidase, an [enzyme](https://www.britannica.com/science/enzyme) that is known to be involved in the breakdown of norepinephrine and serotonin. In cases of severe depression in which therapeutic results are needed quickly, [electroconvulsive therapy](https://www.britannica.com/science/shock-therapy-psychiatry) (ECT) has sometimes proved helpful. In this procedure, a convulsion is produced by passing an [electric current](https://www.britannica.com/science/electric-current) through the person’s brain. For most persons with depression, however, the best therapeutic results are obtained by using a combination of psychotherapy and [antidepressant](https://www.britannica.com/science/antidepressant) medication. (See also [therapeutics](https://www.britannica.com/science/therapeutics/Psychotherapy#ref22261).) Key People: [Viktor Frankl](https://www.britannica.com/biography/Viktor-Frankl) (Show more) Related Topics: [postpartum depression](https://www.britannica.com/science/postpartum-depression) [persistent depressive disorder](https://www.britannica.com/science/dysthymic-disorder) [psychotic depression](https://www.britannica.com/science/psychotic-depression) [Zung Self-Rating Depression Scale](https://www.britannica.com/science/Zung-Self-Rating-Depression-Scale) [Beck Depression Inventory](https://www.britannica.com/science/Beck-Depression-Inventory) (Show more) [See all related content](https://www.britannica.com/facts/depression-psychology) Some persons with depression are affected by treatment-resistant depression (TRD), meaning that they are refractory to existing therapies. For those individuals, scientists have been investigating [alternative](https://www.merriam-webster.com/dictionary/alternative) therapeutic approaches, including [deep brain stimulation](https://www.britannica.com/science/deep-brain-stimulation) (DBS) and [gene therapy](https://www.britannica.com/science/gene-therapy). In DBS, experimental research has focused on the implantation of an electrode in a region of the brain known as the nucleus accumbens, which is located in the striatum (neostriatum) deep within the [cerebral](https://www.merriam-webster.com/dictionary/cerebral) hemispheres and is associated with emotions and feelings such as fear, pleasure, and reward. Studies of depressed animals and postmortem studies of the brains of patients with depression have revealed that reduced levels of a protein known as p11 in cells of the nucleus accumbens are associated with depression. In depressed animals, increasing p11 levels in the nucleus accumbens using gene therapy has been found to relieve depression-like symptoms. Both DBS and gene therapy, however, are associated with potentially dangerous side effects. [The Editors of Encyclopaedia Britannica](https://www.britannica.com/editor/The-Editors-of-Encyclopaedia-Britannica/4419) This article was most recently revised and updated by [Michael Ray](https://www.britannica.com/editor/Michael-Ray/6392). ![Britannica AI Icon](https://cdn.britannica.com/mendel-resources/3-178/images/chatbot/star-ai.svg?v=3.178.5)Britannica AI chevron\_right Depression close [AI-generated answers](https://www.britannica.com/about-britannica-ai) from Britannica articles. AI makes mistakes, so verify using Britannica articles. Load Next Page Feedback Thank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article. verifiedCite While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Select Citation Style Bloom, Floyd E.. "antidepressant". Encyclopedia Britannica, 21 Mar. 2026, https://www.britannica.com/science/antidepressant. Accessed 9 April 2026. 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Accessed 9 April 2026. Copy Citation Share Share to social media [Facebook](https://www.facebook.com/BRITANNICA/) [X](https://x.com/britannica) URL <https://www.britannica.com/science/depression-psychology> External Websites - [World Health Organisation - Depression](https://www.who.int/en/news-room/fact-sheets/detail/depression) - [NHS - Clinical Depression](https://www.nhs.uk/conditions/clinical-depression/) - [American Psychiatric Association - Depression](https://www.psychiatry.org/patients-families/depression) - [The Nemours Foundation - For Parents - Depression](https://kidshealth.org/en/parents/understanding-depression.html) - [Medicine LibreTexts - Depression](https://med.libretexts.org/Courses/Lumen_Learning/Book%3A_Wellness_\(Lumen\)/09%3A_Module_5A-_Mental_and_Emotional_Health/9.04%3A_Depression) - [Verywell Mind - Depression](https://www.verywellmind.com/depression-4157261) - [National Center of Biotechnology Information - Depression](https://www.ncbi.nlm.nih.gov/books/NBK430847/) - [Mayo Clinic - Depression](https://www.mayoclinic.org/diseases-conditions/depression/symptoms-causes/syc-20356007) - [Cleveland Clinic - Depression](https://my.clevelandclinic.org/health/diseases/9290-depression) - [Natural History Museum - Triceratops](https://www.nhm.ac.uk/discover/dino-directory/triceratops.html) Britannica Websites Articles from Britannica Encyclopedias for elementary and high school students. - [depression - Student Encyclopedia (Ages 11 and up)](https://kids.britannica.com/students/article/depression/341189)
Readable Markdown	## News • depression, in [psychology](https://www.britannica.com/science/psychology), a mood or emotional state that is marked by feelings of low self-worth or guilt and a reduced ability to enjoy life. A person who is depressed usually experiences several of the following symptoms: feelings of sadness, hopelessness, or pessimism; lowered [self-esteem](https://www.britannica.com/dictionary/self-esteem) and heightened self-depreciation; a decrease or loss of ability to take pleasure in ordinary activities; reduced energy and vitality; slowness of thought or action; loss of [appetite](https://www.britannica.com/science/appetite); and disturbed [sleep](https://www.britannica.com/science/sleep) or [insomnia](https://www.britannica.com/science/insomnia). Depression differs from simple grief or mourning, which are appropriate emotional responses to the loss of loved persons or objects. Where there are clear grounds for a person’s unhappiness, depression is considered to be present if the depressed mood is disproportionately long or severe vis-à-vis the precipitating event. The distinctions between the duration of depression, the circumstances under which it arises, and certain other characteristics underlie the classification of depression into different types. Examples of different types of depression include [bipolar disorder](https://www.britannica.com/science/bipolar-disorder), [major depressive disorder](https://www.britannica.com/science/major-depressive-disorder) (clinical depression), [persistent depressive disorder](https://www.britannica.com/science/dysthymic-disorder), and [seasonal affective disorder](https://www.britannica.com/science/seasonal-affective-disorder). ## Characteristics and causes of depression Depression is probably the most common psychiatric complaint and has been described by physicians since before the time of ancient Greek physician [Hippocrates](https://www.britannica.com/biography/Hippocrates), who called it [melancholia](https://www.britannica.com/science/melancholia-psychology). The course of the disorder is extremely variable from person to person; it may be mild or severe, [acute](https://www.merriam-webster.com/dictionary/acute) or chronic. Untreated, depression may last an average of four months or longer. Depression is twice as prevalent in women than in men. The typical age of onset is in the 20s, but it may occur at any age. [![Encyclopaedia Britannica thistle graphic to be used with a Mendel/Consumer quiz in place of a photograph.](https://cdn.britannica.com/05/215905-131-626D860A/Encyclopaedia-Britannica-thistle-graphic-logo.jpg) Britannica Quiz 44 Questions from Britannica’s Most Popular Health and Medicine Quizzes](https://www.britannica.com/quiz/44-questions-from-britannicas-most-popular-health-and-medicine-quizzes) Depression can have many causes. Unfavorable life events can increase a person’s vulnerability to depression or trigger a depressive episode. Negative thoughts about oneself and the world are also important in producing and maintaining depressive symptoms. However, both psychosocial and biochemical mechanisms seem to be important causes; the chief biochemical cause appears to be the defective regulation of the release of one or more naturally occurring [neurotransmitters](https://www.britannica.com/science/neurotransmitter) in the [brain](https://www.britannica.com/science/brain), particularly [norepinephrine](https://www.britannica.com/science/norepinephrine) and [serotonin](https://www.britannica.com/science/serotonin). Reduced quantities or reduced activity of these chemicals in the brain is thought to cause the depressed mood in some sufferers. Depression is also associated with disordered [rapid eye movement (REM) sleep](https://www.britannica.com/science/rapid-eye-movement-sleep). A region of the brain known as the [amygdala](https://www.britannica.com/science/amygdala) contains [neurons](https://www.britannica.com/science/neuron) that project into the [brainstem](https://www.britannica.com/science/brainstem) and appear to be involved in modulating REM sleep. The amygdala is also associated with processing negative thoughts and may be enlarged, hyperactive, or otherwise dysfunctional in some depressed persons. Although the significance of these associations is [yet](https://www.britannica.com/dictionary/yet) to be defined, the link between depression, disordered REM sleep, and abnormalities of the amygdala has led to new avenues of research into the neurobiology and treatment of depression. Research suggests that depression is also linked to [physical activity](https://www.britannica.com/topic/physical-activity), whereby physical activity may lower a person’s risk of developing depression. Individuals who [exercise](https://www.britannica.com/topic/exercise-physical-fitness) typically report better [mental health](https://www.britannica.com/science/mental-hygiene) and are less likely to be depressed, compared with individuals who do not exercise. ## Types of depression [Bipolar disorder](https://www.britannica.com/science/bipolar-disorder), major depressive disorder, and persistent depressive disorder are the primary types of depression. A person who experiences alternating states of depression and [mania](https://www.britannica.com/science/mania) (abnormal elevation of mood) or hypomania (distinct, though not necessarily abnormal, elevation of mood) is said to suffer from bipolar disorder. [Major depressive disorder](https://www.britannica.com/science/major-depressive-disorder) is [characterized](https://www.britannica.com/dictionary/characterized) by severe symptoms that disrupt the individual’s daily life, typically with effects on appetite, sleep, work, or the ability to enjoy life. Episodes of major depression can occur at any age and may occur once or multiple times in an affected person’s life. [Persistent depressive disorder](https://www.britannica.com/science/dysthymic-disorder) involves symptoms that last two or more years, sometimes marked by episodes of major depression. Smart, reliable knowledge for professionals, students, and curious minds everywhere. [SUBSCRIBE](https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=inline-cta&utm_campaign=smart-2026) ![Penguin, ship, mountain, atlas](https://cdn.britannica.com/marketing/inline-left.webp) ![shohei ohtani, plants, andy wharhol art](https://cdn.britannica.com/marketing/inline-right.webp) ![Mobile](https://cdn.britannica.com/marketing/inline-mobile.webp?w=400) Other types of depression include postpartum depression, psychotic depression, and seasonal affective disorder, each of which develops under specific circumstances. [Postpartum depression](https://www.britannica.com/science/postpartum-depression) develops in women in the period following [childbirth](https://www.britannica.com/science/birth). Symptoms include [anxiety](https://www.britannica.com/science/anxiety), a lack of interest in caring for the infant, and feelings of sadness, hopelessness, or inadequacy. Postpartum depression is longer-lasting and more severe than the “baby blues,” a common condition among women after childbirth that typically involves mood swings, feelings of sadness, and crying spells. Psychotic depression arises against a background of [psychosis](https://www.britannica.com/science/psychosis), which may involve symptoms of [delusions](https://www.merriam-webster.com/dictionary/delusions), hallucinations, or [paranoia](https://www.britannica.com/science/paranoia). [Seasonal affective disorder](https://www.britannica.com/science/seasonal-affective-disorder) is characterized by the onset of depressive symptoms in autumn and winter, which are [alleviated](https://www.merriam-webster.com/dictionary/alleviated) with increased exposure to natural light in spring and summer. ## Treatments for depression There are three main treatments for depression. The two most important—and widespread by far—are [psychotherapy](https://www.britannica.com/science/psychotherapy) and psychotropic [medication](https://www.britannica.com/science/drug-chemical-agent), specifically [antidepressants](https://www.britannica.com/science/antidepressant) such as [bupropion](https://www.britannica.com/science/bupropion). Psychotherapy aims to alter the patient’s maladaptive [cognitive](https://www.merriam-webster.com/dictionary/cognitive) and behavioral responses to stressful life events while also giving emotional support to the patient. Antidepressant medications, by contrast, directly affect the chemistry of the brain and presumably achieve their therapeutic effects by correcting the chemical dysregulation that is causing the depression. Two types of medications, [tricyclic antidepressants](https://www.britannica.com/science/tricyclic-antidepressant-drug) and [selective serotonin reuptake inhibitors](https://www.britannica.com/science/selective-serotonin-reuptake-inhibitor) (SSRIs; e.g., fluoxetine \[[Prozac](https://www.britannica.com/science/Prozac)\]), though chemically different, both serve to prevent the presynaptic reuptake of serotonin (and in the case of tricyclic antidepressants, norepinephrine as well). This results in the buildup or accumulation of neurotransmitters in the brain and allows them to remain in contact with the [nerve cell](https://www.britannica.com/science/neuron) receptors longer, thus helping to elevate the patient’s mood. By contrast, the antidepressants known as [monoamine oxidase inhibitors](https://www.britannica.com/science/monoamine-oxidase-inhibitor) (MAOIs) interfere with the activity of monoamine oxidase, an [enzyme](https://www.britannica.com/science/enzyme) that is known to be involved in the breakdown of norepinephrine and serotonin. In cases of severe depression in which therapeutic results are needed quickly, [electroconvulsive therapy](https://www.britannica.com/science/shock-therapy-psychiatry) (ECT) has sometimes proved helpful. In this procedure, a convulsion is produced by passing an [electric current](https://www.britannica.com/science/electric-current) through the person’s brain. For most persons with depression, however, the best therapeutic results are obtained by using a combination of psychotherapy and [antidepressant](https://www.britannica.com/science/antidepressant) medication. (See also [therapeutics](https://www.britannica.com/science/therapeutics/Psychotherapy#ref22261).) Some persons with depression are affected by treatment-resistant depression (TRD), meaning that they are refractory to existing therapies. For those individuals, scientists have been investigating [alternative](https://www.merriam-webster.com/dictionary/alternative) therapeutic approaches, including [deep brain stimulation](https://www.britannica.com/science/deep-brain-stimulation) (DBS) and [gene therapy](https://www.britannica.com/science/gene-therapy). In DBS, experimental research has focused on the implantation of an electrode in a region of the brain known as the nucleus accumbens, which is located in the striatum (neostriatum) deep within the [cerebral](https://www.merriam-webster.com/dictionary/cerebral) hemispheres and is associated with emotions and feelings such as fear, pleasure, and reward. Studies of depressed animals and postmortem studies of the brains of patients with depression have revealed that reduced levels of a protein known as p11 in cells of the nucleus accumbens are associated with depression. In depressed animals, increasing p11 levels in the nucleus accumbens using gene therapy has been found to relieve depression-like symptoms. Both DBS and gene therapy, however, are associated with potentially dangerous side effects. This article was most recently revised and updated by [Michael Ray](https://www.britannica.com/editor/Michael-Ray/6392).
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