Background. Prevalence and co-occurrence of mental disorders is high among patients consulting their family general practitioner (GP) for a new health problem, but data on diagnostics and sociodemographics are sketchy.

Method. A cross-sectional two-phase epidemiological study. A total of 1785 consecutive patients with new complaints, aged 18–65 years, consulting 28 family practices during March–April 2000 in Aarhus County, Denmark were screened, in the waiting room, for mental and somatic symptoms with SCL-8 and SCL-Somatization questionnaires, for illness worry with Whitely-7 and for alcohol dependency with CAGE. In a stratified random sample of 701 patients, physician interviewers established ICD-10 diagnoses using the SCAN interview. Prevalence was calculated using weighted logistic regression, thus correcting for sample skewness.

Results. Half of the patients fulfilled criteria for an ICD-10 mental disorders and a third of these for more than one group of disorders. Women had higher prevalence of somatization disorder and overall mental disorders than men. Men had higher prevalence of alcohol abuse and hypochondriasis than women. Psychiatric morbidity tended to increase with age. Prevalence of somatoform disorders was 35·9% (95% CI 30·4–41·9), anxiety disorders 16·4% (95% CI 12·7–20·9), mood disorders 13·5% (95% CI 11·1–16·3), organic mental disorders 3·1% (95% CI 1·6–5·7) and alcohol abuse 2·2% (95% CI 1·5–3·1). Co-morbidities between these groups were highest for anxiety disorders, where 89% also had another mental diagnosis, and lowest for somatoform disorders with 39%.

Conclusions. ICD-10 mental disorders are very prevalent in primary care and there is a high co-occurrence between most disorders. Somatoform disorders, however, more often than not exist without other mental disorders.