Improvements are necessary for three reasons. First, light therapy doesn’t work for everyone. Studies have reported that 50% to 80% of patients achieve complete relief and that remission may depend upon carefully individualized timing of light exposure. Second, dosing remains a major question. The recommendation for 30 minutes of daily exposure to 10,000 lux is based on average response to white light. Finally, side effects, while mild for many patients, may be more of a concern for others.

Dr. Michael Miller, editor in chief of the Harvard Mental Health Letter, notes that investigations are now under way to see if changing the timing or type of light therapy might improve response or reduce side effects. Some areas of study:

Better timing. Researchers reported that remission from SAD was twice as likely if light therapy was precisely calibrated to melatonin rhythms which may vary by several hours from one individual to the next.

Dawn simulation. In this variation, a preset light device turns on before a patient awakens. Light intensity increases gradually over a period of 90 minutes. Although studies so far have been small, they have also been promising.

Blue light. Studies have found that cells in the retina are particularly sensitive to blue light, suggesting that this wavelength may powerfully affect circadian rhythms. Researchers are investigating whether blue light might provide the same benefit as white light but with less exposure time.

Source: Harvard Health Publications

SAD was first noted before 1845, but was not officially named until the early 1980′s. As sunlight has affected the seasonal activities of animals (i.e., reproductive cycles and hibernation), SAD may be an effect of this seasonal light variation in humans. As seasons change, there is a shift in our “biological internal clocks” or circadian rhythm, due partly to these changes in sunlight patterns. This can cause our biological clocks to be out of “step” with our daily schedules. The most difficult months for SAD sufferers are January and February, and younger persons and women are at higher risk.

Symptoms Include:

• regularly occurring symptoms of depression (excessive eating and sleeping, weight gain) during the fall or winter months.
• full remission from depression occur in the spring and summer months.
• symptoms have occurred in the past two years, with no nonseasonal depression episodes.
• seasonal episodes substantially outnumber nonseasonal depression episodes.
• a craving for sugary and/or starchy foods.

POSSIBLE CAUSE OF THIS DISORDER

Melatonin, a sleep-related hormone secreted by the pineal gland in the brain, has been linked to SAD. This hormone, which may cause symptoms of depression, is produced at increased levels in the dark. Therefore, when the days are shorter and darker the production of this hormone increases.

TREATMENTS

Phototherapy or bright light therapy has been shown to suppress the brain’s secretion of melatonin. Although, there have been no research findings to definitely link this therapy with an antidepressant effect, many people respond to this treatment. The device most often used today is a bank of white fluorescent lights on a metal reflector and shield with a plastic screen. For mild symptoms, spending time outdoors during the day or arranging homes and workplaces to receive more sunlight may be helpful. One study found that an hour’s walk in winter sunlight was as effective as two and a half hours under bright artificial light.

If phototherapy doesn’t work, an antidepressant drug may prove effective in reducing or eliminating SAD symptoms, but there may be unwanted side effects to consider. Discuss your symptoms thoroughly with your family doctor and/or mental health professional.