Predictors of response and nonresponse to light treatment for winter depression.

OBJECTIVE The authors' goal was to determine whether the pattern and severity of depressive symptoms predict response to light treatment for seasonal affective disorder. METHOD Subjects with winter depression (N = 103) were given bright light treatment. Seventy-one were classified as responders, 15 as nonresponders, and 17 as partial responders. Using depression rating scale data and correlational and multivariate analysis, the authors sought predictors of response in baseline symptom and scale scores. RESULTS Responders were characterized by atypical symptoms, especially hypersomnia, afternoon or evening slump, reverse diurnal variation (evenings worse), and carbohydrate craving. By contrast, nonresponders were characterized mainly by melancholic symptoms, retardation, suicidality, depersonalization, typical diurnal variation (mornings worse), anxiety, early and late insomnia, appetite loss, and guilt. The ratio of atypical to classical symptoms of depression, rather than severity per se, best predicted treatment outcome for the group as a whole. Pretreatment expectations were positively correlated with improvement on the Hamilton Depression Rating Scale but not on a supplementary scale of atypical symptoms. CONCLUSIONS Light-responsive seasonal affective disorder is distinguished by a dominant atypical symptom profile closely associated with depressed mood. Nonresponders from a clinically distinct group with melancholic features. The patient's symptom profile, therefore, should be considered when diagnosing seasonal affective disorder and selecting treatment.