Treatment of seasonal affective disorder with high-intensity light. A phototherapy study with an Icelandic group of patients.

The standard phototherapy procedure for seasonal affective disorder (SAD) has been to expose patients to 2500 lux light intensity for 2 h. This study investigated whether high-intensity light treatment with a brief exposure time would relieve symptoms of SAD. Ten SAD patients were randomly assigned to 40-min exposure to 10,000 lux white light or to 400 lux red light which served as placebo. Each patient received treatment for 8 days, and after a wash-out period was crossed over to the other treatment condition. Depression was assessed by the 21-item HDRS and SIGH-SAD by a blind rater and the patients completed the BDI for self-assessment. Significantly greater improvement was found with 10,000 lux treatment than with the placebo (P = 0.011, P = 0.017 and P = 0.028 for SIGH-SAD, HDRS and BDI respectively). The 10,000 lux therapy improved the SIGH-SAD score by an average of 16.1 while the average improvement on placebo treatment was 5.0. The patients were rated again the following summer; most of them were the symptomless. Those patients who improved most on phototherapy also tended to improve most during the summer.