Prevalence of psychiatric disorder in a methadone maintenance population

The objective of this study was to examine the prevalence of psychiatric disorders in a group of patients who had recently entered a methadone maintenance programme.

A total of 62 patients were interviewed using the Composite International Diagnostic Interview (CIDI) within 6 months of commencing methadone maintenance. The CIDI was used to establish symptoms of psychiatric illness at interview and in the 12 months prior.

In the 12 months prior to interview, 76% of the sample fulfilled ICD-10 criteria for a psychiatric disorder other than substance-use disorder. Over half of the group interviewed fulfilled ICD-10 criteria for an affective disorder, two-thirds fulfilled criteria for an anxiety disorder and just under half fulfilled diagnostic criteria for both an affective disorder and an anxiety disorder in the 12 months prior to interview. At the time of interview, 19% fulfilled ICD-10 diagnostic criteria for a moderate or severe affective disorder. Seventy per cent of males and 89% of females interviewed had a comorbid psychiatric illness. In 71% of the group who had a comorbid psychiatric illness, the onset of psychiatric symptomatology was reported to predate the use of heroin.

The prevalence of psychiatric disorder is up to 10 times higher in the population on methadone maintenance than in the general population and is two to three times higher than that found in community surveys of those with a substance-use disorder. These results are consistent with earlier findings and have implications for service planning.