MDD — Major Depressive Disorder

Major Depressive Disorder (MDD) is the most common and clearly defined clinical form of depression under the DSM-5. It is diagnosed when a person has at least 5 of the following symptoms over a two-week period, with at least one being depressed mood or loss of interest/pleasure: depressed mood for most of the day, markedly diminished interest or pleasure in nearly all activities (anhedonia), changes in weight or appetite, insomnia or hypersomnia, observable agitation or psychomotor slowing, fatigue or loss of energy, feelings of worthlessness or excessive guilt, difficulty concentrating, and recurrent thoughts of death or suicide.

MDD affects an estimated 5–8% of adults worldwide in any given year — well over 280 million people globally. It is the leading cause of disability worldwide according to the World Health Organization. Unlike ordinary sadness, MDD does not require an identifiable cause, persists beyond two weeks, and significantly interferes with daily functioning (work, relationships, self-care).

With adequate treatment (a combination of psychotherapy and medication), 70–80% of patients show significant improvement. Left untreated, episodes tend to last 6 to 12 months and to recur.