major depressive disorder

Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Introduced by a group of US clinicians in the mid-1970s, 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), and has become widely used since. The disorder causes the second-most years lived with disability, after lower back pain.

The diagnosis of major depressive disorder is based on the person's experiences, and behavior reported by family or friends, and a mental status examination. There is no laboratory test for the disorder, but blood testing and similar may be done to rule out physical conditions that can cause similar symptoms. The most common time of onset is in a person's 20s. Men are much less likely to report than women, with approximately 33.2% of men and 43.0% of women with depressive symptoms reporting seeking help, possibly due to pressures of masking for men. The course of the disorder varies widely, from one episode lasting months to a lifelong disorder with recurrent episodes.