Seasonal and non-seasonal depression and the five-factor model of personality

The purpose of this study was to compare the personality characteristics of patients with non-psychotic, major depression, seasonal subtype (SAD) to patients with non-psychotic, major depression, without seasonality (non-SAD). The patients were consecutive referrals to a university-affiliated mood disorders outpatient clinic. The personality characteristics were assessed using the five-factor model of personality (FFM) as measured by the revised NEO Personality Inventory (NEO PI-R). Patients were assessed during the acute depressive episode. Controlling for severity of depression, differences were found on only one of the five dimensions, with the SAD patients (n = 43) scoring significantly higher on the Openness dimension than non-SAD patients (n = 57). Based on these results we infer SAD patients may represent a psychologically distinct subgroup of depressed patients-more imaginative, more emotionally sensitive and likely to entertain unconventional ideas than non-SAD patients. This personality constellation may explain why individuals with SAD are more sensitive to and may amplify the mild dysphoria typically associated with winter months.