Types of Depression

The three types of depressive episode are single, recurrent, and seasonally patterned. Depression is further classified as mild, moderate, severe with psychosis, severe without psychosis, in partial remission, in full remission, chronic, and unspecified.

Single—Single episode depression means that a person experiences finite depression, according to the criteria for diagnosis, but does not suffer from it again.

Recurrent—Recurrent depression is defined by sub-criteria:

  • Two or more depressive episodes, each separated by at least 2 months of return to more or less usual functioning (If there has been a previous major depressive episode, the current episode of depression need not meet the full criteria for major depressive disorder.)
  • Has never had a manic episode or an unequivocal hypomanic episode

DSM-IV, Diagnostic and Statistical Manual of Mental Disorders, ed. 4. Washington DC: American Psychiatric Association (APA). 1994. For a description of hypomanic episode, see cyclothymia.

Seasonal Affective Disorder (SAD)—Fluctuations in mood in depressed people may be season-related. People with season-related depression are usually depressed during the fall and winter, and become healthier in spring and summer. Although rare, some become depressed in spring and summer, and healthier in the fall and winter. The cause for this may be a result of reduced melatonin secretion in the brain. Melatonin secretion is triggered by sunlight, which is sparse during winter, especially in places where winter days are shortest.

Seasonally patterned depression also has a sub-set of diagnostic criteria:

  • There has been a regular temporal relationship between the onset of an episode of bipolar disorder (including bipolar disorder NOS) or recurrent major depression (including depressive disorder NOS) and a particular 60-day period of the year (e.g., regular appearance of depression between the beginning of October and the end of November). Note: Do not include cases in which there is an obvious effect of seasonality related to psychosocial stressors (e.g., regularly being unemployed every winter).
  • Full remissions (or a change from depression to mania or hypomania) also occurred within a particular 60-day period of the year (e.g., depression disappears from mid-February to mid-April).
  • There have been at least three episodes of mood disturbance in 3 separate years that demonstrate the temporal seasonal relationship defined in A and B; at least 2 of the years were consecutive.

DSM-IV, Diagnostic and Statistical Manual of Mental Disorders, ed. 4. Washington DC: American Psychiatric Association (APA). 1994.

The criteria provide for the seasonal occurrence of depression and mania. Diagnosis requires observable periods of remission and a three-year past of occurrence. Treatment of SAD may involve phototherapy to influence melatonin secretion and regulate sleep patterns.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 03 Feb 2001

Last Modified: 20 Jun 2013