What is seasonal affective disorder (SAD)?
Seasonal affective disorder (SAD) is a type of depression that occurs at the same time each year. SAD most often begins in the fall or winter and then subsides in the spring. It sometimes is called the "winter blues" because most people with seasonal affective disorder have an episode of depression during the winter months, although it is possible to experience SAD during summer months. A diagnosis of SAD is made when a pattern of depression and remission from depression is present for at least two consecutive years.
What are the symptoms of SAD?
SAD consists of four central features:1
Recurring major depressive episodes that begin around the same time each year (usually in September or October) and end around the same time each year (usually in April or May)
Full recovery from the symptoms during "nonseasonal" months (usually May through August)
Depressive episodes that occur during the same time of year for 2 consecutive years
Over the lifetime course of the illness, more depressive episodes during winter months than summer months
What causes seasonal affective disorder (SAD)?
The specific cause of SAD is not clearly understood. However, lack of sunlight caused by the shorter and darker days of winter, darkened or indoor workplaces, and long cloudy spells have been linked to episodes of depression in people with SAD. Some experts think SAD may be caused by a disturbance in the body's natural biological clock (circadian rhythms) or problems with the regulation of a brain chemical (neurotransmitter) called serotonin.1
Who gets SAD?
You are more prone to develop seasonal affective disorder (SAD) if you are:2, 1
Female. 60% to 90% of people diagnosed with SAD are women
An older teen or young adult. Young people are at higher risk for winter depressive episodes. The risk of developing SAD for the first time decreases as you grow older.
Living far from the equator. People who live in the northern hemisphere develop seasonal affective disorder more often, although you can develop SAD no matter where you live.
Working at a certain job or living in a situation that keeps you out of sunlight (such as working at night and sleeping during the daylight hours).
What happens when SAD develops?
People with SAD who have episodes of depression in the winter usually live in areas far away from the equator, where there are shorter days in the winter months. You may be at higher risk for developing SAD if you live in areas such as Alaska and other northern states in the United States; Canada; or Scandinavian countries, although you can get SAD no matter where you live. You will usually begin to get symptoms of depression in the fall, need treatment throughout the winter, and get better in the spring and summer as the days lengthen.
Less is known about seasonal affective disorder in which episodes of depression occur in the summer. Symptoms of summer SAD usually appear in late spring or early summer and resolve in the fall. Summer SAD may be related to excessive heat and humidity rather than a lack of sunlight. If you have summer SAD, you may be irritable or have no energy in the summer months.
How is SAD diagnosed?
A diagnosis of SAD is made when a pattern of depression and remission from depression is present for at least two consecutive years. Your health professional can diagnose SAD through a combination of a physical examination, medical history, and possibly a mental health assessment or questionnaire that helps identify symptoms of SAD. A family history of SAD increases your risk of developing SAD.
SAD can be difficult to distinguish from major depression.
Can SAD be treated?
There is no known cure for SAD, but the depressive episodes of SAD can be managed effectively with medications, counseling, light therapy, or a combination of these treatments.