Primary mood disorder characterized by a sustained feeling of sadness and/or decreased interest in all or most activities once enjoyed, which represents a change from previous state


The 12-month and lifetime prevalence of major depressive disorder (MDD): 10.4% and 20.6%, respectively (1); predominant age: low risk before early teens; highest prevalence in teens and young adults

Etiology and Pathophysiology

Diverse theories regarding the pathophysiology

Twin studies suggest 37% concordance.

Risk Factors

  • Female > male (2:1)
  • Adverse life events (2)
  • First-degree relative with depression, bipolar, suicide, substance abuse; spouse with depression
  • Presence of comorbid medical conditions including neurodegenerative diseases

Commonly Associated Conditions

Bipolar disorder, cyclothymic disorder, grief reaction, anxiety disorders, somatoform disorders, schizophrenia/schizoaffective disorders, conduct disorder, substance abuse

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