Sa. Morrissey et al., SEASONAL AFFECTIVE-DISORDER - SOME EPIDEMIOLOGIC FINDINGS FROM A TROPICAL CLIMATE, Australian and New Zealand Journal of Psychiatry, 30(5), 1996, pp. 579-586
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.