SEASONAL AFFECTIVE-DISORDER - SOME EPIDEMIOLOGIC FINDINGS FROM A TROPICAL CLIMATE

Objective: To determine whether a predominantly summer-focussed patter n of seasonal affective disorder (SAD) exists in tropical northern Aus tralia. Method: A mail survey containing a modified form of the Season al Pattern Assessment Questionnaire (SPAQ) was administered to 176 hou seholds in the city of Townsville (latitude: 19 degrees south). Result s: Using previously reported screening criteria, 9% of respondents rep orted a degree of summer impairment indicative of SAD, while the incid ence rate for winter SAD was 1.7%. This summer-winter ratio is typical ly reversed in more temperate latitudes. Conclusions: Excessive heat a nd humidity were reported to be the two most influential environmental factors affecting mood and behaviour. It is likely that respondents m eeting criteria for summer SAD represent the extreme end of a spectrum of summer-related mood and behaviour change that affects many individ uals in northern Australia. Strategies for further clinical and epidem iological research on SAD in tropical climates are proposed.