Child and adolescent psychiatric disorders in a public service over seventy years

The entire sample of N=45554 patients attending the child and adolescent psychiatric service of the Canton of Zurich, Switzerland between 1921 and 1990 was analyzed with regard to age, sex, and diagnoses. Data were based on annual reports of the institution for the period between 1921 and 1978. From 1979 onwards, electronically stored data on each patient were available. ICD-9 diagnoses were applied between 1979 and 1987. The ICD-10 system was introduced in 1988. The total administrative prevalence rate varied between 0.15 and 0.40 percent with an increasing trend over time. On the average, boys outnumbered girls by a sex ratio of 2:1. The age distribution showed peaks at 8 to 9 years and during adolescence. The distributions of the most common diagnoses showed remarkable differences over time. It is assumed that changes in diagnostic categories rather than changes in true prevalence rates play a major role in the latter trend.