Seasonal affective disorder and latitude of living

Aim - Since the importance of latitude of living for the prevalence of Seasonal Affective Disorder (SAD) is unclear, the study aims to test the latitude hypothesis by comparing SAD in two rather similar groups of students living at latitudes far apart. Methods - Two groups of students, 199 in Tromso, Norway (690 N) and 188 in Ferrara, Italy (440 N) were asked to fill in the Seasonal Pattern Assessment Questionnaire. Results - Global Seasonality score (GS-score) was significantly higher in Italian than in Norwegian students, in females and in students with sleeping-problems. Norwegian students had significantly higher SAD prevalence in winter and in spring. Most people in both countries felt worst in October and November, and the prevalence of Autumn SAD was not significantly different between the two countries. Conclusions - The hypothesis that SAD is linked to amount of environmental light and latitude of living was not supported.