Trends in socio-economic differences in self-reported depression during the years 1979-2002 in Finland.

BACKGROUND: Socio-economic differences in depressive symptoms are well reported, but there are only few studies concerning changes in these differences over time. The aim of this study was to assess trends in socio-economic differences in self-reported depression over the time period 1979-2002 in Finland.
METHODS: The data source was a representative repeated cross sectional survey "Health Behaviour and Health among the Finnish Adult Population" (AVTK) linked with socio-economic register data from Statistics Finland, for the period 1979-2002. The age group of 25-64 years was included in this study (N = 71,290; average annual response rate 75%). Outcome measure was a single question of self-reported depression. Socio-economic factors included education, employment status and household income. The main analyses were conducted by multiple logistic regression.
RESULTS: The prevalence of self-reported depression fluctuated in both men and women but remained higher in women compared to men over the past 24 years. After adjusting for age, socio-economic differences in self-reported depression were clear in regard to education, employment status and household income over the time period 1979-2002. When all socio-economic factors were mutually adjusted for, the association with self-reported depression remained significant in the unemployed, the retired and in those in the lowest household income categories in both genders. The effect of education on self-reported depression was mediated by the other socio-economic factors. Based on a time trend analysis, the socio-economic differences in self-reported depression remained stable over the time period 1979-2002.
CONCLUSIONS: Socio-economic inequalities in self-reported depression were confirmed, and they have persisted with approximately the same magnitude over the past 24 years.