Early response to light therapy partially predicts long-term antidepressant effects in patients with seasonal affective disorder

Objective: To determine if the antidepressant effect of 1 hour of light therapy is predictive of the response after 1 and 2 weeks of treatment in patients with seasonal affective disorder (SAD). Patients: Twelve patients with SAD. Setting: National Institutes of Health Clinical Center, Bethesda, Md. Interventions: Light therapy for 2 weeks. Outcome measures: Scores on the Seasonal Affective Disorder Version of the Hamilton Depression Rating Scale (SIGH-SAD) on 4 occasions (before and after 1 hour of light therapy and after 1 and 2 weeks of therapy) in the winter when the patients were depressed. Change on typical and atypical depressive scores at these time points were compared. Results: Improvement of atypical depressive symptoms after 1 hour of light therapy positively correlated with improvement after 2 weeks of therapy. Conclusion: In patients with SAD, the early response to light therapy may predict some aspects of long-term response to light therapy, but these results should be treated with caution until replicated.