The gloom of winter seems to get inside some people, with the dark affecting their moods as well as their days. Known as seasonal affective disorder (SAD), this form of depression affects about 1% to 2% of the population. Although it strikes all genders and ages, women are more likely to develop SAD than men, and young people are more likely to develop it than older people.
SAD seems to be triggered by decreased exposure to daylight. Typically, it arrives during the fall or winter months and subsides in the spring. Symptoms are similar to general depression and include lethargy, loss of interest in once-pleasurable activities, interpersonal problems, irritability, inability to concentrate, and changes in sleeping patterns, appetite, or both.
Experts don't fully understand the cause of SAD, but leading theories place the blame on an out-of-sync body clock or on improper levels of either the hormone melatonin or the neurotransmitter serotonin.
The mainstay of SAD treatment is light therapy, also called phototherapy. Phototherapy involves daily sessions of sitting close to a special light source that is far more intense than normal indoor light. The recommendation is typically to get 30 minutes of exposure to light at an intensity of 10,000 lux each day, but optimum dosing remains a major question. Some people need more light exposure than this, others need less.
The light must enter through the eyes to be effective; skin exposure doesn't seem to work. Some people feel better after only one light treatment, but most people require at least a few days of treatment, and some need several weeks. You do not need a prescription to purchase a light box to treat SAD; however, it's best to work with a professional to monitor the benefits of the treatment.
Some SAD light boxes look like medical equipment, while others are more like regular table lamps. The prices vary. Although professional groups and government agencies endorse light therapy, your insurance company may balk. If you are counting on coverage, you better check first.
For additional advice on light therapy for SAD and other ways to improve your mood and alleviate depression, buy Understanding Depression, a Special Health Report from Harvard Medical School.