ABSTRACT
BACKGROUND: The aim of the present study was to assess the prevalence of seasonal affective disorder (SAD) in The Netherlands. METHODS: The subjects (n = 5356), randomly selected from community registers, were given the Seasonal Pattern Assessment Questionnaire and the Centre for Epidemiological Studies Depression Scale over a period of 13 months. The response rate was 52.6%. RESULTS: Three percent of the respondents met the criteria for winter SAD, 0.1% for summer SAD. The criteria for subsyndromal SAD, a milder form of SAD, were met by 8.5%, 0.3% of whom showed a summer pattern. Younger women received a diagnosis of SAD more often than men or older women. CONCLUSIONS: SAD subjects were significantly more often unemployed or on sick leave than other subjects. Respondents who met winter SAD criteria were significantly more depressed than healthy subjects, in both winter and summer. Finally, month of completion had no influence on the number of subjects meeting the SAD criteria.
Subject(s)
Seasonal Affective Disorder/epidemiology , Absenteeism , Adolescent , Adult , Age Distribution , Aged , Environment , Female , Humans , Male , Middle Aged , Netherlands/epidemiology , Population Surveillance , Prevalence , Prospective Studies , Retrospective Studies , Seasonal Affective Disorder/diagnosis , Seasons , Severity of Illness Index , Sex Distribution , Time Factors , WorkABSTRACT
BACKGROUND: The aim of the study is to investigate the relationship between the prevalence of SAD and latitude. METHODS: An overview of the epidemiological literature on the prevalence of SAD is given and studies relevant for the latitudinal dependency of prevalence will be analyzed and discussed. RESULTS: The mean prevalence of SAD is two times higher in North America compared to Europe. Over all prevalence studies, the correlation between prevalence and latitude was not significant. A significant positive correlation was found between prevalence and latitude in North America. For Europe there was a trend in the same direction. CONCLUSIONS: The influence of latitude on prevalence seems to be small and other factors like climate, genetic vulnerability and social-cultural context can be expected to play a more important role. Additional controlled studies taking these factors into account are necessary to identify their influence.
