Influence of phototherapy treatment duration for seasonal affective disorder: outcome at one vs. two weeks.

Most previous phototherapy research has been conducted on trials of 1 week duration. This study compares response to phototherapy at weeks 1 and 2. All subjects (n = 26) were between 18 and 65 years and met Diagnostic and Statistical Manual of Mental Disorders, 3rd ed, revised, (DSM III-R) criteria for major depression, recurrent, seasonal pattern and had a Hamilton Depression Rating Scale score (HAM-D) > or = 20. A rater blinded to treatment schedule and study hypothesis repeated the HAM-D-31 1 and 2 weeks after baseline to assess treatment response to bright light. Response rates at week 1 defined by 50% reduction in HAM-D-31 and HAM-D-31 score < 8 were 62% and 27%, respectively. At week 2, however, 65% had a 50% reduction in HAM-D-31 and 62% had a HAM-D-31 < score 8 (chi-square = 6, p = 0.01). Four patients (15%) who were nonresponders at week 1 responded after 2 weeks. The results show a statistically different outcome after 2 weeks of treatment and suggest the necessity of longer trials of phototherapy.