A LONGITUDINAL FOLLOW-UP-STUDY OF SEASONAL AFFECTIVE-DISORDER

Objective: The purposes of this study were to evaluate the long-term s tability of a seasonal pattern of recurrent depression, identify possi ble factors associated with alteration of the seasonal pattern, and de termine whether atypical vegetative symptoms during early seasonal dep ressive episodes predict future seasonal relapses. Method: The subject s were 41 patients satisfying the criteria used in the Japanese multic enter study of seasonal affective disorder who were consistently treat ed at the same outpatient clinic. Their longitudinal courses were eval uated by using case records and the Schedule for Affective Disorder an d Schizophrenin-Lifetime Version; the mean follow-up period was 10.4 y ears. Results: Nine subjects (22.0%) consistently showed a fall-winter pattern of recurrence throughout follow-up. Seventeen patients with a n initial fall-winter pattern subsequently tended to shift seasons or show less seasonality. This alteration in pattern was possibly associa ted with antidepressant therapy or life events. Eleven patients with a n initial diagnosis of nonseasonal affective disorder subsequently dev eloped seasonal affective disorder; no specific factors were associate d with this change. Atypical vegetative symptoms were significantly mo re common in patients with stable seasonal patterns of recurrence than in those who lost seasonality. Conclusions: Although seasonal affecti ve disorder appeared to be altered by antidepressant treatment, the pr esence of a core group of patients with a consistent seasonal pattern of recurrent depression suggests the validity of seasonal affective di sorder as a distinct subtype of recurrent affective illness. The findi ngs also suggest that atypical vegetative symptoms during early season al depressive episodes predict the subsequent seasonality of depressio n.