Use of health care services by patients with co-occurring severe mental illness and substance use disorders

To better respond to health care needs of people with co-occurring mental illness and substance use disorders, it is vital to understand their itinerary through the health care system. The objective of this article is to describe the characteristics of service utilization among patients with co-occurring disorders in a large urban area and to assess how homogeneous this population is, in terms of service utilization. Methodologically, we used a sample (N=5,467) constituted from administrative and clinical databases. Those identified as having substance use disorders and severe mental illness were followed over 12 months with respect to their utilization of medical services. A descriptive analysis of the data and a two-step cluster analysis were carried out. The analysis confirmed a relatively high utilization of emergency services, ourpatient clinics, private practices and hospitalization among patients with co-morbidity. This is most likely explained by the clinical complexity of the cases and the multiple problems associated with dual diagnoses, but is also evidence of the fact that these patients are not treated according to best practice guidelines, which recommend a comprehensive and integrated approach which deals with both diagnoses. Cluster analysis allowed us to extract certain clinical profiles that are associated with specific service utilization patterns. These demonstrate the heterogeneity within this population. In conclusion, this study demonstrates the need to develop strategies for organizing health care and services that are adapted to various sites of service utilization and to diverse profiles of patients with co-occurring mental illness and substance use disorders.