Major depressive disorder (MDD), also known simply as depression, is a mental disorder[9] characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Those affected may also occasionally have delusions or hallucinations.[1] Introduced by a group of US clinicians in the mid-1970s,[10] the term was adopted by the American Psychiatric Association for this symptom cluster under mood disorders in the 1980 version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) classification, and has become widely used since.
The diagnosis of major depressive disorder is based on the person's reported experiences and a mental status examination.[11] There is no laboratory test for the disorder, but testing may be done to rule out physical conditions that can cause similar symptoms.[11] The most common time of onset is in a person's 20s,[3][4] with females affected about twice as often as males.[4] The course of the disorder varies widely, from one episode lasting months to a lifelong disorder with recurrent major depressive episodes.
Those with major depressive disorder are typically treated with psychotherapy and antidepressant medication.[1] Medication appears to be effective, but the effect may only be significant in the most severely depressed.[12][13] Hospitalization (which may be involuntary) may be necessary in cases with associated self-neglect or a significant risk of harm to self or others. Electroconvulsive therapy (ECT) may be considered if other measures are not effective.[1]
Major depressive disorder is believed to be caused by a combination of genetic, environmental, and psychological factors,[1] with about 40% of the risk being genetic.[5] Risk factors include a family history of the condition, major life changes, certain medications, chronic health problems, and substance use disorders.[1][5] It can negatively affect a person's personal life, work life, or education as well as sleeping, eating habits, and general health.[1][5] Major depressive disorder affected approximately 163 million people (2% of the world's population) in 2017.[8] The percentage of people who are affected at one point in their life varies from 7% in Japan to 21% in France.[4] Lifetime rates are higher in the developed world (15%) compared to the developing world (11%).[4] The disorder causes the second-most years lived with disability, after lower back pain.[14]
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