Few South American studies have examined current prevalence rates of psychiatric disorders.

To examine prevalence rates in a nationally representative adult population from Chile.

The Composite International Diagnostic Interview was administered to a stratified random sample of 2978 individuals from four provinces representative of the country's population. Six-month and 1-month prevalence rates were estimated. Demographic correlates, comorbidity and service use were examined.

Nearly a fifth of the Chilean population had had a psychiatric disorder during the preceding 6 months. The 6-month and 1-month prevalence rates were 19.7% and 16.7% respectively. For the 6-month prevalence the five most common disorders were simple phobia, social phobia, agoraphobia, major depressive disorder and alcohol dependence. Less than 30% of those with any psychiatric diagnosis had a comorbid psychiatric disorder and the majority of them had sought treatment from mental health services.

Current prevalence studies are useful indicators of service needs. People with comorbid psychiatric conditions have high rates of service use. The low rate of comorbidity in Chile merits further study.