Background: The long-term course of seasonal affective disorder has not been well studied.
Method: Using the Structured Clinical Interview for DSM-III-R, we interviewed 75% of a sample of 124 subjects diagnosed from five to eight years previously as fulfilling DSM-III-R criteria for recurrent major affective disorder, seasonal pattern.
Results: In the follow-up period, 38% of the sample continued to fulfil DSM-III-R criteria for seasonal illness; 28% had recurrent major depressive disorder, but no longer displayed a seasonal pattern; 18% were completely well with no further depression; 6% had subsyndromal symptoms; and 5%, although not meeting DSM-III-R criteria for seasonal illness, were still displaying constant periodicity. A short duration of index episode and a high frequency of illness predicted a continuing seasonal course of illness.
Conclusion: Diagnostic criteria for seasonal affective disorder need to be further refined, possibly restrictively, if they are to be used to predict the future course of seasonal illness.