An Observational, Mixed-Design, Exploratory Study Evaluating Cognitive Function and Structural Deficits in Seasonal Affective Disorder

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Summary

SAD patients showed persistent cortical thinning in the frontal lobe and volumetric reductions in the globus pallidus across both summer and winter, suggesting structural brain changes that are not purely seasonal. Cognitive deficits in set-shifting, psychomotor speed, and executive function were paradoxically more detectable in summer, likely because healthy controls showed winter cognitive fluctuations that masked differences, with implications for timing of light therapy and cognitive support interventions.

Key Findings

SAD patients (N=17) showed widespread significant cortical thinning in the frontal lobe present in both summer and winter seasons
Significant volumetric reductions in the globus pallidus were observed in SAD patients compared to healthy controls (N=17)
Cognitive impairments in set-shifting, psychomotor speed, and executive function were detected in SAD patients during summer months but not winter months
Cognitive deficits in winter may have been masked by seasonal cognitive fluctuations in healthy control participants
Structural deficits were located in key limbic system nodes responsible for top-down mood regulation and cognitive control