The strongest clinical data are for bright light therapy, a method that has been investigated for over two decades in well over a thousand patients. In 1998, Dr. Michael Terman and colleagues published a definitive study using the most efficient, timesaving treatment regimen for bright light, a level of 10,000 lux for 30 minutes daily upon awakening. The apparatus uses a bank of high-output fluorescent bulbs that are shielded behind a smooth diffusing filter that eliminates all UV radiation as a safety measure. The lights tilt toward the eyes from above, minimizing unpleasant glare. SAD patients who used the light box upon awakening did significantly better than those who used it in the evening, although a small minority found evening light to be superior.
Also in fall 1998, a group of 13 Canadian specialists issued a set of professional consensus guidelines for the treatment of SAD. Among their conclusions:
- The starting "dose" for light therapy using a fluorescent light box is 10,000 lux for 30 minutes per day.
- Alternatively, light boxes emitting 2,500 lux require two hours of exposure per day.
- Light therapy should be started in the early morning, upon awakening, to maximize treatment response.
- Response to light therapy often occurs within one week, but some patients may require up to four weeks to show a response.
- Common side effects of light therapy include headache, eyestrain, nausea and agitation, but these effects are generally mild and transient, or disappear with reducing the dose of light.
Sources:
Lam, R.W., and A.J. Levitt. "Canadian consensus guidelines for the treatment of seasonal affective disorder: a summary of the report of the Canadian Consensus Group on SAD." Canadian Journal of Diagnosis 15 Suppl. (1998): S1-S15.
Terman M, Terman JS, Ross DC. "A controlled trial of bright light and negative air ionization for treatment of winter depression." Archives of General Psychiatry 55 (1998): 875-882.
