Psychiatric epidemiology in a sample of 1510 ten-year-old children--I. Prevalence.

Prevalence estimates of psychiatric disorder in 10-yr-old rural Norwegian children were based on responses to symptom checklists for parents and teachers. The parents' index showed highest validity, and was used as a basis for prevalence estimates. Properties of the index were shown to be sample specific, and a validity test should consequently always be administered to representative subsamples in psychiatric epidemiological studies based on symptom checklists. Prevalence of functional problems of a primarily psychological nature was calculated by proportional extrapolations from the validity test results. The prevalence rate for the total sample was 5%, and corrected prevalence when emigrants were excluded was 4.6%.