Seasonal affective disorder and non-seasonal affective disorders: Results from the NESDA study

Abstract

Background Seasonal affective disorder (SAD) is considered to be a subtype of depression. Aims To compare the clinical picture of SAD to non-seasonal affective disorders (non-SADs). Method Diagnoses according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) were established in 2185 participants of the Netherlands Study of Depression and Anxiety. The Seasonal Pattern Assessment Questionnaire was administered to diagnose SAD. Symptoms of depression and anxiety were measured with the Inventory of Depressive Symptoms, the Beck Anxiety Inventory and the Fear Questionnaire. Results Participants with SAD, participants with a lifetime bipolar disorder and participants with a lifetime comorbid anxiety and depressive disorder scored highest in terms of psychopathology in the past year. The seasonal distribution of major depressive episodes was not different for participants with or without SAD. Conclusions SAD may be a measure of severity of depression with a subjectively perceived worsening of symptoms in the winter months.