The effects of motivational interviewing on patients with comorbid substance use admitted to a psychiatric emergency unit - a randomised controlled trial with two year follow-up

BACKGROUND The prevalence of substance use in people acutely admitted to in-patient psychiatric wards is high and the patients` duration of stay is limited. Motivational interviewing is a method with evidence based effect in short interventions. The aims of the present study were to compare the effects of 2 sessions of motivational interviewing and treatment as usual (intervention group) with treatment as usual only (control group) on adult patients with comorbid substance use admitted to a psychiatric in-patient emergency unit. METHODS This was an open randomised controlled trial including 135 patients where substance use influenced the admittance. After admission and assessments, the patients were allocated to the intervention group (n = 67) or the control group (n = 68). The primary outcome was self-reported days per month of substance use during the last 3 months at 3, 6, 12 and 24 months after inclusion. Data was analysed with a multilevel linear repeated measures regression model. RESULTS Both groups reduced substance use during the first 12 months with no substantial difference between the 2 groups. At 2 year follow-up, the control group had increased their substance use with 2.4 days (95% confidence interval (CI) -1.5 to 6.3), whereas the intervention group had reduced their monthly substance use with 4.9 days (95% CI 1.2 to 8.6) compared to baseline. The 2 year net difference was 7.3 days of substance use per month (95% CI 1.9 to 12.6, p < 0.01) in favour of the intervention group. CONCLUSIONS The present study suggests that 2 sessions of motivational interviewing to patients with comorbid substance use admitted to a psychiatric emergency unit reduce substance use frequency substantially at 2 year follow-up. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT00184223.