How common is seasonal affective disorder in temperate Australia? A comparison of BDI and SPAQ estimates

Background: The frequency of winter Seasonal Affective Disorder (SAD) in temperate Australia is unknown. Method: A random community sample in Melbourne completed four waves of data collection (winter and summer across two years). The presence of winter SAD was estimated in three ways: (i) self-reports on the Seasonal Pattern Assessment Questionnaire (SPAQ), (ii) evidence of significant depression as assessed on the Beck Depression Inventory (BDI) in winters and not summers, and (iii) a combined definition based on both SPAQ and BDI estimates. Results: Of 1080 questionnaires originally mailed, complete four-wave BDI data was obtained from 380 respondents, and complete SPAQ data from 297. The frequency of winter SAD as estimated from SPAQ data was 0.7% and from BDI data was 0.5%. One participant (1 of 297, 0.3%) met BDI criteria and approached caseness on SPAQ criteria. Limitations: A larger sample is necessary to definitively estimate prevalence. Conclusions: Winter SAD appears to be rare in temperate Australia. The best estimate from the current study (0.3%) is an advance on simple self-report estimates and provides a necessary reference point for clinicians and researchers.