major depressive disorder

noun

: a serious mood disorder involving one or more episodes of intense psychological depression or loss of interest or pleasure that lasts two or more weeks and is accompanied by irritability, fatigue, poor concentration, sleep disturbances, weight gain or loss, feelings of worthlessness or guilt, and sometimes suicidal tendencies : clinical depression, major depression

About 18 million Americans are diagnosed with a major depressive disorder each year.

—David Schwab

The most serious form of depression is major depressive disorder, characterized by depressed mood, loss of interest or pleasure, changes in appetite, increased or decreased sleep, increased or decreased motor activity, fatigue, feelings of worthlessness or guilt, difficulty concentrating and, for some people, recurrent thoughts of death or suicide.

—Sandi Lloyd

—abbreviation MDD

Examples of major depressive disorder in a Sentence

Recent Examples on the Web

Conditions such as major depressive disorder, bipolar disorder, post-traumatic stress disorder, schizophrenia and severe anxiety disorders frequently involve fluctuating symptoms. —Jeffrey Freedman, Sun Sentinel, 27 Apr. 2026

Specifically, the companies are investigating psilocybin as a therapy for treatment-resistant depression and for major depressive disorder; methylone is being studied as a potential treatment for PTSD. —Claire Cameron, Scientific American, 24 Apr. 2026

The companies are studying psilocybin for treatment-resistant depression and major depressive disorder and methylone for post-traumatic stress disorder (PTSD). —Mary Kekatos, ABC News, 24 Apr. 2026

The agency will grant priority review vouchers specifically to Compass’ psilocybin product for treatment-resistant depression, Usona’s similar medicine for major depressive disorder, and an MDMA-like treatment for post-traumatic stress disorder from Transcend. —Elaine Chen, STAT, 24 Apr. 2026

Word History

First Known Use

1975, in the meaning defined above

Rhymes for major depressive disorder

• boarder
• border
• corder
• order
• warder
• camcorder
• recorder
• reorder
• suborder
• transborder

Medical Definition

major depressive disorder

noun

: a serious mood disorder involving one or more episodes of intense psychological depression or loss of interest or pleasure that lasts two or more weeks and is accompanied by irritability, fatigue, poor concentration, sleep disturbances, weight gain or loss, feelings of worthlessness or guilt, and sometimes suicidal tendencies : clinical depression, major depression

The diagnosis of both major depressive disorder and subsyndromal symptoms is complicated by difficulties that elderly patients may have in recognizing or describing depressive symptoms.

—Lawrence M. Martin et al., The John Hopkins White Papers

—abbreviation MDD