SAD is a form of depression triggered by decreased exposure to daylight. It arrives during fall or winter and subsides in the spring, affecting 1% to 2% of the population. It strikes all ages and genders but is more prevalent among women and younger persons.
Like general depression, its symptoms include lethargy, loss of interest in once-enjoyable activities, interpersonal problems, irritability, inability to concentrate, and changes in sleeping patterns, appetite, or both.
Leading theories for the cause of SAD are an out-of-sync clock or improper levels of either the hormone melatonin or the neurotransmitter serotonin.
The favored treatment is phototherapy (light therapy), which involves daily sessions of sitting near a special light source far more intense than normal indoor light. The light must enter the eye; skin exposure isn’t effective.
Generally, the recommendation is to get 30 minutes exposure daily to light at an intensity of 10,000 lux, but optimum frequency of dosing depends on the individual—some people need only a few treatments to feel better, while others need several weeks.
You don’t need a prescription to buy a light box, but it’s best to work with a professional to monitor and adjust treatment.
My Take on the subject: I was taken aback by the stats of 1% to 2% of the population being afflicted with SAD because I had been also taken aback by the number of my acquaintances who’ve told me they’re affected by SAD—it’s a much higher percentage than what Harvard gives. Perhaps people are mistakenly self-diagnosing SAD for other forms of depression that need different palliative treatment.
Source: Harvard Medical School Healthbeat, December 6, 2012