Research on Seasonal Affective Disorder (SAD) has produced several etiologicalmodels of SAD symptomatology, including a common cause model... Show moreResearch on Seasonal Affective Disorder (SAD) has produced several etiologicalmodels of SAD symptomatology, including a common cause model that conceptualizessymptoms as the result of a single underlying disease process, and the Dual VulnerabilityModel (Young et al., 1991) which posits that psychological symptoms of depressionfollow the onset of vegetative symptoms (e.g. hypersomnia, increased appetite) inindividuals with a vulnerability to seasonal changes. Studies of the structure of SADsymptomatology have been limited in their ability to evaluate these models. This studyused exploratory factor analysis and network analysis to examine baseline winter SADsymptoms (using a modified BDI-II) in 177 adults participating in a randomizedcontrolled trial of light treatment and CBT for SAD (Rohan et al., 2015). The factoranalysis supported a four-factor model that included negative cognition/affect, loss ofvitality, dysregulation, and increases in weight/appetite. The complex network model ofSAD conceptualized the network as a system of interacting symptoms. Results of thenetwork model paralleled those of the factor analysis in producing four communities ofinter-correlated symptoms. In addition to the full symptom network, a directed acyclicgraph was constructed to model causal relations between symptoms. Results suggest thatvegetative symptoms (loss of vitality and appetite/weight) lead ultimately to cognitivesymptoms, with intermediate effects of dysregulation symptoms. This partially supportsthe Dual Vulnerability model. Findings from the factor analysis and the network analysisare compared, and their implications for and treatment of SAD is discussed. Show less
