Date of Award


Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)




Sandra T. Sigmon

Second Committee Member

Jeffrey E. Hecker

Third Committee Member

Michael Robbins


Recent literature on Seasonal Affective Disorder (SAD) has begun to focus on diathesis stress models, including Young and colleagues' (1 991) Dual Vulnerability Hypothesis (DVH). The DVH 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. Such a model addresses SAD as well as non-seasonal depression, and suggests that there may be an as yet unidentified group suffering fiom only the biological vulnerability (i.e., winter anergia). However, until very recently few studies have directly tested this model, and most have focused on the possible psychological mechanisms related to mood symptoms (e.g., McCarthy et al., 2002; Young & Azam, 2003). Research has demonstrated a temporal relation between and mood and vegetative symptoms, with vegetative symptoms having an earlier onset than mood symptoms (McCarthy et al., 2002; Young et al., 1991) 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, attentional bias) that may represent part of the psychological vulnerability shared by SAD sufferers. Furthermore, the present study represents the first attempt to recruit and classify individuals with winter anergia (i.e., individuals possessing only a biological vulnerability component). Sixty-seven individuals participated in the study across three groups, individuals with a history of SAD (i.e., SAD-HX), history of winter anergia (i.e., WA) and with no history of depression. Findings supported the DVH, with an early vegetative symptom onset than mood symptom for the SAD-HX group. SAD-HX group participants also evidenced more ruminative responses and negative automatic thoughts about the seasons. Findings are generally supportive of Young et al.'s (1991) DVH and directions for future research are suggested.

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