Co-morbidity and cannabis use in a mental health trust in South East England

The prevalence of co-morbidity (severe mental illness and substance) may be less in rural and semi-rural areas than inner cities. The aims were therefore to measure the prevalence of co-morbidity among patients of attending a mental health service in a semi-rural area South East England.

Cross-sectional prevalence survey of 1,808 patients with detailed assessments from a representative sample of 373 patients identified as having a combination of severe mental illness and substance misuse. Interviews with key workers were performed using validated methods from the COSMIC study.

The response rates equalled or exceeded 90% for the various parts of the study. One-tenth of patients attending the Community Mental Health Teams (CMHTs) reported problematic use of illicit drugs and 17% reported alcohol problems in the past year. 22% of Community Drug and Alcohol Service (CDAS) clients reported a severe mental illness and 46% reported some other form of psychiatric disorder. Of patients with a combined diagnosis of mental illness and substance misuse, cannabis use was 4-fold more common amongst patients attending the CMHT than CDAS (33% vs. 8%) while use of amphetamine was five-fold higher in the CMHT group (10% vs. 2%). Patients with concurrent psychiatric and substance misuse problems represent a similar proportion of the aggregate caseload of both treatment services with observed prevalence amongst the CDAS and CMHT patients with a diagnosis for anxiety disorder (18% vs. 26%), minor depression (42% vs. 32%), personality disorders (32% vs. 36%), histories of self-harm (52% vs. 46%) and violence (33% vs. 30%) respectively.

Co-morbidity is common in clients amongst CMHT and CDAS clients although use of cannabis was significantly more common in CMHT clients than in CDAS clients.