A comparison of open treatment of seasonal major and minor depression with light therapy

Background: Although several investigators have described a milder form of seasonal affective disorder (SAD), called subsyndromal SAD, little is known about the effect of light therapy in this group. The current study evaluates 3 weeks of open treatment with light therapy in SAD and subsyndromal SAD patients. Methods: Subjects with major or minor depression according to DSM-IV with a seasonal pattern were recruited during the winter of 1998–1999 from clinic patients and media advertising. Subjects were commenced on open treatment of morning light therapy, for 30 min daily using a new fluorescent light therapy unit that produced approximately 5000 lux at a distance of 12 inches. The treatment lasted 3 weeks and at the end of the first and second week of treatment the duration of exposure could be increased to a maximum of 60 min at the discretion of the clinician. The Structured Interview Guide for the Hamilton Depression Rating Scale-SAD version (SIGH-SAD) was administered weekly to evaluate outcome. Response was defined in a variety of ways to reflect the fact that subsyndromal SAD subjects had milder symptoms. Results: Forty-six subjects entered treatment and 44 (SAD, n=29, subsyndromal SAD, n=15) completed at least 2 weeks. Response rates were generally similar in SAD subjects (64–69%) and subsyndromal SAD (40–67%) patients. There was a trend for longer exposure to be associated with better outcome. Conclusions: Light therapy may be an effective treatment for subjects with both major and minor depression with a seasonal pattern. Optimal duration, for the light therapy unit used in this study, is likely 45–60 min daily.