Seasonal depression, often called seasonal affective disorder (SAD), is a depression that occurs each year at the same time, usually starting in fall, worsening in winter, and ending in spring. It is more than just “the winter blues” or “cabin fever.” A rare form of SAD, known as “summer depression,” begins in late spring or early summer and ends in fall.
What are the symptoms of seasonal affective disorder?
People who suffer from SAD have many of the common signs of depression, including:
- loss of interest in usual activities
- withdrawal from social activities
- inability to concentrate
- extreme fatigue and lack of energy
- a “leaden” sensation in the limbs
- increased need for sleep
- craving for carbohydrates, and accompanying weight gain.
Symptoms of summer SAD include:
- weight loss
- agitation and restlessness
- trouble sleeping
- decreased appetite
How common is SAD?
Approximately one half million of the U.S. population suffers from winter SAD, while 10 to 20 percent may suffer from a more mild form of winter blues. Three-quarters of the sufferers are women, and the onset typically is early adulthood. SAD also can occur in children and adolescents. Older adults are less likely to experience SAD.
This illness is more commonly seen in people who live in cloudy regions or at high latitudes (geographic locations farther north or south of the equator). Individuals who relocate to higher latitudes are more prone to SAD.
What causes seasonal affective disorder?
The exact cause of this condition is not known, but evidence to date strongly suggests that—for those with an inherent vulnerability—SAD is triggered by changes in the availability of sunlight. One theory is that with decreased exposure to sunlight, the internal biological clock that regulates mood, sleep, and hormones is shifted. Exposure to light may reset the biological clock.
Another theory is that brain chemicals that transmit information between nerves, called neurotransmitters (for example, serotonin), may be altered in individuals with SAD. It is believed that exposure to light can correct these imbalances.
How can I tell if I have seasonal affective disorder?
It is very important that you do not diagnose yourself. If you have symptoms of depression, see your doctor for a thorough assessment. Sometimes physical problems can cause depression. But other times, symptoms of SAD are part of a more complex psychiatric problem. A mental health professional typically can evaluate your pattern of symptoms and identify whether you have SAD or another type of mood disorder.