A randomised controlled trial of outpatient versus inpatient integrated treatment of dual diagnosis patients: a failed but informative study

Abstract

The co-occurrence of severe mental illness (SMI) and substance use disorder (SUD) in dual diagnosis patients is common and associated with negative treatment outcomes. Therefore, integrated treatments, combining proven effective mental health and substance abuse interventions, have emerged. However, evidence about the effectiveness of integrated outpatient versus inpatient treatment for dual diagnosis patients from randomised controlled trials is lacking. The aim of the paper is to determine whether integrated outpatient treatment for patients with SMI and SUD is more effective than integrated inpatient treatment. Three months of post-treatment hospitalisation, problem drug use and psychiatric status were assessed in 82 patients with SMI and SUD in a randomised controlled trial (RCT) comparing five months of integrated inpatient treatment (n = 40) with five-months integrated outpatient treatment (n = 42) following a shared one-month inpatient stabilisation phase. No significant differences in outcomes were found between the two treatment conditions using intention-to-treat analyses. However, considerable crossover of patients between treatment conditions occurred. This crossover occurred significantly more in the outpatient treatment group, where patients remained in inpatient treatment longer than the intended one month stabilisation phase. As a consequence, actual time in inpatient treatment did not differ between the study groups. Post hoc analyses showed that baseline patient characteristics did not predict actual time in inpatient treatment. Due to considerable crossover of study participants, we were unable to answer our study question regarding the comparative effectiveness of inpatient versus outpatient treatment. This raises serious questions regarding the feasibility of RCTs investigating inpatient versus outpatient integrated treatment in patients with SMI and co-occurring SUD.

Keywords:

• severe mental illness
• substance use disorder
• integrated inpatient treatment
• integrated outpatient treatment
• randomised controlled trial

Acknowledgements

This study was granted by ZonMw, the Netherlands. The authors thank all patients for their participation to the study and Renee Zwart and her colleagues for collecting the data. Also, the authors acknowledge the assistance of Daphne van Hoeken (PhD) for preparing the first version of the database and report. Chris van der Meer (MD) is thanked for his contributions to the study. The study was approved by the medical–ethical committee for research in mental health care settings in the Netherlands (METiGG). All participants provided written informed consent.