Seasonal affective disorder (SAD)

Seasonal affective disorder (SAD) is a form of depression that occurs in relation to the seasons, most commonly beginning in winter.

Causes
Seasonal affective disorder (SAD) is marked by symptoms of depression profound enough to seriously affect work and relationships. The disorder may have its onset in adolescence or early adulthood and, like other forms of depression, occurs more frequently in women than in men. Most people with the "winter blahs" or "cabin fever" do not have SAD.
The cause of SAD is not known, but is thought to be related to numerous factors including body temperature, hormone regulation, and ambient light. A rare form occurs in the summer

Symptoms
Depression with the onset of fall or winter
Lack of energy
Decreased interest in work or significant activities
Increased appetite with weight gain
Carbohydrate cravings
Increased sleep and excessive daytime sleepiness
Social withdrawal
Afternoon slumps with decreased energy and concentration
Slow, sluggish, lethargic movement

Signs and Tests
A psychological evaluation rules out other causes for the symptoms and confirms the diagnosis.

Treatment
As with other types of depression, antidepressant medications and talk therapy can be effective. Light therapy using a special lamp to mimic the spectrum of light from the sun may also be helpful.
Symptoms commonly resolve on their own with the change of seasons.