Massachusetts General Hospital

Seasonal Affective Disorder

What is seasonal affective disorder?

Seasonal affective disorder, or SAD, is a mood disorder characterized by depression related to a certain season of the year – especially winter. However, SAD is often not described as a separate mood disorder but as a "specifier," referring to the seasonal pattern of major depressive episodes that can occur within major depression and manic depression.

SAD is a clinical diagnosis accepted in the medical community. Dr. Norman E. Rosenthal, Chief of Environmental Psychiatry Branch of the National Institute of Mental Health Disorders, is the researcher credited with discovering SAD.

Who is affected by SAD?

Onset usually occurs during adulthood (with the average onset occurring at approximately age 23), and is four times more likely to affect women than men. According to the National Mental Health Disorders Association, approximately 10 to 20 percent of the population suffers from mild winter SAD, and nearly 5 percent suffer from a more severe form of the disorder.

What are the symptoms of seasonal affective disorder?

Two seasonal patterns of symptoms have been identified with SAD: a fall-onset type, also called "winter depression," in which major depressive episodes begin in the late fall to early winter months and remit during the summer months, and a spring-onset type, also called "summer depression," in which the severe depressive episode begins in late spring to early summer. The following are the most common symptoms of SAD. However, each individual may experience symptoms differently. Symptoms may include:

• Increased sleep and daytime drowsiness

• Irritability

• Fatigue, or low energy level

• Decreased sex drive

• Diminished concentration

• Difficulty thinking clearly

• Increased appetite, especially for sweets and carbohydrates causing weight gain

The symptoms of SAD may resemble other psychiatric conditions. Always see your health care provider for a diagnosis.

What causes SAD?

Decreased sunlight is thought to be part of the cause of SAD, and is under clinical investigation.

Treatment for seasonal affective disorder

Specific treatment for SAD will be determined by your health care provider based on:

• Your age, overall health, and medical history

• Extent of the disease

• Your tolerance for specific medications, procedures, or therapies

• Expectations for the course of the disease

• Your opinion or preference

The treatments for "winter depression" and "summer depression" often differ, and may include any, or a combination, of the following:

• Light therapy

• Antidepressant medications

• Psychotherapy, such as cognitive behavioral therapy or interpersonal therapy