Service use and costs of people with dual diagnosis in South London

To compare the service use and costs of individuals who have a dual diagnosis of psychosis and substance abuse with those who have a diagnosis of psychosis but no substance abuse.

Patients with psychosis were identified and a representative sample were interviewed. Six-month service use was measured and costs calculated. Regression models were developed to predict costs from background characteristics and dual diagnosis status.

A greater proportion of the patients with dual diagnosis used community psychiatric nurses, in-patient care and the emergency clinic. The regression analysis revealed that dual diagnosis patients had significantly higher 'core' psychiatric service costs (a difference of pound sterling 1362) and non-accommodation service costs (pound sterling 1360) than non-dual-diagnosis patients. The difference when all services were analysed was pound sterling 1046, but this was not statistically significant.

Specific interventions for dual diagnosis patients should be introduced and assessed in terms of individual outcomes, service use and costs.