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



  • Lifetime prevalence of major depressive disorder (MDD) is 20.6% (1).
  • Low risk before early teens; highest prevalence in teens and young adults; average age of onset is 30 years.

Etiology and Pathophysiology

Pathophysiology is poorly understood.

Twin studies suggest 37% concordance.

Risk Factors

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

General Prevention

Physical activity lowers the risk of depression (3).

Commonly Associated Conditions

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

There's more to see -- the rest of this topic is available only to subscribers.