Background. The aim of this study was to determine differences between patients attending primary-care clinics with somatic symptoms for which no organic cause can be found, and those with a clear organic basis for their complaints.

Methods. Physical and psychiatric morbidity was measured in 5447 subjects presenting for primary care in 14 countries. Subjects were recruited using a two-stage design from 26969 consecutive attenders and 25916 (96·5%) subjects were successfully screened using the General Health Questionnaire (GHQ-12). The response rate for the second-stage assessment was 63% and consisted of the Composite International Diagnostic Instrument adapted for use in primary care (CIDI-PHC), the 28-item GHQ, the Groningen Social Disability Schedule (GSDS) and GP ratings to assess physical psychiatric and social status. Patients who reached the threshold for the number of somatic symptoms (five or more symptoms) were then divided into two groups on the basis of whether their somatic symptoms were medically explained or not.

Results. The presence of somatic symptoms, irrespective of aetiology, was associated with increased social and psychiatric morbidity. In the case of non-medically explained symptoms there was a clear linear relationship while with medically explained symptoms psychiatric morbidity rose sharply in the presence of more than 11 symptoms. Patients who had five or more non-medically explained symptoms were significantly younger, had greater psychiatric morbidity, were at greater risk of harmful use of alcohol and reported greater social disability than those with a medical explanation for their somatic symptoms. Patients who had an excess of somatic symptoms in both categories had especially high rates of social and psychiatric morbidity.

Conclusions. These results show a strong association between somatic symptoms irrespective of aetiology and psychiatric morbidity across disparate cultures.