Stability of prevalences of mental disorders in a normal population cohort followed for 16 years.

Results from the Finnish UKKI study on longitudinal changes in prevalences of different mental disorder categories in a population cohort (n = 723) are presented. The subjects were investigated three times: in the original survey during 1969-71, and in two follow-ups (5 and 16 years after the original survey). The prevalence of all mental disorders was about 30% in all phases of the study, although the prevalence of psychoses increased from 1.1% to 3.5%. A special focus of interest was the changes in different 10-year birth cohorts during the 16 years. The results indicated that the youngest birth cohort (born in 1945-54) did not reach the same prevalence level of all mental disorders combined as the birth cohort 10 years older upon reaching the same age.