Validation of the Seasonal Pattern Assessment Questionnaire (SPAQ).

The validity of the Seasonal Pattern Assessment Questionnaire (SPAQ) was examined by interviewing 81 individuals who had participated in an earlier community survey of seasonal affective disorder (SAD) in Iceland. When SAD and subsyndromal SAD (S-SAD) were combined into a 'winter problem' group, the questionnaire's sensitivity, specificity and positive predictive value for that group were 94%, 73% and 45%, respectively. The SPAQ discriminated poorly between SAD and S-SAD, and hence it had a poor case-finding ability for SAD. Clinical evaluation verified a diagnosis of SAD in individuals who had no previous information about this syndrome. The questionnaire furthermore identified a group of individuals who had generalized anxiety and marked seasonal variations. Clinical evaluation arrived at a similar prevalence rate of SAD as the questionnaire.