Seasonal affective disorder

Seasonal affective disorder (SAD), also called winter depression, winter blues, summer depression and seasonal depression, is a mood disorder that happens in people who have normal mental health throughout most of the year. They show depressive symptoms at the same time each year, usually in the winter.
Cause and Symptoms.
Some people think that SAD is related to not having enough serotonin because they don't get enough sunlight, which could cause serotonin polymorphisms. Serotonin polymorphisms could be the cause in SAD, although it has been disputed (people think it's not correct).
Some symptoms are:
Treatment.
Treatments include light therapy, medication, ionized-air administration, cognitive-behavioral therapy, and taking the hormone melatonin at the right time. Doctors often cure SAD with bright light therapy, although normal light therapy is the most common treatment for SAD. Part of light therapy can include being in sunlight, either directly from being outside, or by using a computer controlled heliostat (a device that includes a mirror, usually a plain mirror, usually turns to keep reflecting sunlight on a specific object) to reflect into the windows of a home or office. Physical exercise is also a good form of therapy for SAD, especially when combined with other forms of treatments.