Ruminative response style and the severity of seasonal affective disorder

Research generally has supported the hypothesis of the Response Style Theory that a ruminative response style is associated with a greater severity of depression episodes. However, no published research has applied this theory to seasonal affective disorder (SAD). We examined the relationship between response style and severity of winter symptoms in a longitudinal study of individuals previously diagnosed with SAD. Eighteen participants kept accounts of their mood and their responses to mood for 14 consecutive days in the fall. Statistical modeling of these data yielded measures of response style for each participant. Ruminative response style, but not distracting response style, predicted symptom severity in winter, controlling for severity in the fall. As suggested by the Dual Vulnerability Hypothesis of SAD, ruminative response style interacted with fall vegetative symptom severity to predict winter nonvegetative symptom severity. Results also suggest that distracting response style may consist of two different types of response.