Epidemiology of major depression in a predominantly rural health region

Background: Several large-scale cross-sectional studies have evaluated the prevalence of major depression in Canadian populations. Few studies have employed prospective methods, which are necessary to evaluate incidence, and few have focused on predominantly rural areas. Methods: Subjects who had participated in a cross-sectional general health survey were invited to participate in a second wave of data collection 6 months later. These subjects were recontacted using a telephone interview. A brief diagnostic instrument for major depression was used in both waves,and a variety of other variables relevant to the epidemiology of major depression were measured. Results: Of 801 subjects initially enrolled, 666 (83.1%) consented to be recontacted, and 501 (75.2%) of these were successfully reached. The incidence of major depression was 3.8%. The incidence was higher in women, although this difference did not attain statistical significance. Having a past history of depression and having a high level of perceived stress were predictors of risk. An exploratory comparison with data collected using similar methods in a nearby urban centre determined that the rural prevalence was lower than urban, and that a variety of factors (street drugs, deficits in social support, unemployment, recent life events) may contribute have to this difference. Conclusions: The 6-month cumulative incidence of depressive disorder was much higher than that reported by most previous studies. This may be a result of the diagnostic instrument employed, which captures a broader spectrum of depressive morbidity than the instruments used in most previous studies. Also, as the study did not exclude subjects with previous depressive episodes during their lifetime, the incidence rate reflects risks of major depressive episodes rather than major depressive disorders.