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