Seasonal Affective Disorder

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Seasonal affective disorder (also called SAD) is a type of depression that follows the seasons. The most common type of SAD is called winter depression. It usually begins in late fall or early winter and normal mood returns in summer. A less common type of SAD, known as summer depression, usually begins in the late spring or early summer. SAD may be related to changes in the amount of daylight you get.

Seasonal affective disorder is estimated to affect 10 million Americans. Another 10 percent to 20 percent may have mild SAD. SAD is more common in women than in men. Illness typically begins around age 20. Some people experience symptoms severe enough to affect quality of life, and 6 percent require hospitalization. Many people with SAD report at least one close relative with a psychiatric disorder, most frequently a severe depressive disorder (55 percent) or alcohol abuse (34 percent). Although some children and teenagers get SAD, it usually doesn't start in people younger than age 20. Yet when it does the syndrome is first suspected by parents and teachers. Risk decreases with age. SAD is more common the farther north you live.

Seasonal Affective Disorder. Last reviewed 09/29/2006


  • American Psychiatric Association
  • Diagnostic and Statistical Manual of Mental Disorders, 4th Edition
  • What is seasonal affective disorder?
  • National Alliance of Mental Illness
  • National Institute of Mental Health
  • U.S. Department of Health and Human Services; 2005
  • National Mental Health Association
  • American Family Physician
  • Substance Abuse and Mental Health Services Administration