Mood disorders are common. In the most recent surveys, major depressive disorder has the highest lifetime prevalence (almost 17 percent) of any psychiatric disorder. The lifetime prevalence rate of different forms of DSM-IV-TR unipolar depressive disorder, according to the eight major community surveys, are shown in Table 1.


The yearly incidence of a major depression is 1.59 percent (women, 1.89 percent; men, 1.10 percent). The lifetime prevalence rates of different clinical forms of bipolar disorder are shown in Table 2. The annual incidence (number of new cases) of a major depressive episode is 1.59 percent (women, 1.89 percent; men, 1.10 percent). The annual incidence of bipolar illness is less than 1 percent, but it is difficult to estimate, because milder forms of bipolar disorder are often missed.

Table 1 Lifetime Prevalence Rates of Depressive Disorders

Type Lifetime Prevalence (%) Major depressive episode Range 5-17 Average 12 Dysthymic disorder Range 3-6 Average 5 Minor depressive disorder Range 10 Average - Recurrent brief depressive disorder Range 16 Average - Full unipolar spectrum 20-25 (Adapted from Rihmer Z, Angst A. Mood Disorders: Epidemiology. In: Sadock BJ, Sadock VA, eds. Comprehensive Textbook of Psychiatry. 8th ed. Baltimore: Lippincott Williams & Wilkins; 2004, with permission.)

Table Lifetime Prevalence Rates of Bipolar I, Bipolar II, Cyclothymic Disorder, and Hypomania

Lifetime Prevalence (%) Bipolar I disorder 0-2.4 Bipolar II disorder 0.3-4.8 Cyclothymia 0.5-6.3 Hypomania 2.6-7.8 Full bipolar spectrum 2.6-7.8 (Adapted from Rihmer Z, Angst A, Mood Disorders: Epidemiology. In: Sadock BJ, Sadock VA, eds. Comprehensive Textbook of Psychiatry. 8th ed. Baltimore: Lippincott Williams & Wilkins; 2004, with permission.)