Recent literature on seasonal affective disorder (SAD) has begun to focus on diathesis-stress models, including Young and colleagues' dual vulnerability hypothesis. The dual vulnerability hypothesis posits that individuals must possess both a biological vulnerability to developing vegetative symptoms and a psychological vulnerability to developing mood symptoms in order to develop SAD episodes. However, few studies have directly tested this model until very recently. Research has demonstrated a temporal relation between mood and vegetative symptoms, with vegetative symptoms having an earlier onset than mood symptoms supporting the idea that separate factors related to the two symptom clusters exist. The current study represents a longitudinal assessment of vegetative and mood symptoms, as well as cognitive factors (i.e., rumination, automatic thoughts) that may represent part of the psychological vulnerability shared by SAD sufferers. Furthermore, the present study represents only the second to assess state levels of cognitive factors that may impact recurrent SAD episode severity. Fifty-one individuals participated in the study across two groups, individuals with a history of SAD, and with no history of depression or SADs. Findings supported the dual vulnerability hypothesis, with an early vegetative symptom onset than mood symptom evident for the individuals with a history of SAD. Participants with a history of SAD also reported more ruminative responses and negative automatic thoughts about the seasons. Findings are generally supportive of Young and colleagues' dual vulnerability hypothesis and directions for future research are suggested.