Cost-Effectiveness of Motivational Interviewing to Reduce Alcohol and Cannabis Use Among Patients With Depression

Motivational interviewing (MI) is a promising intervention for helping patients with mental health problems reduce their substance use. Examining the cost-effectiveness of MI and associations between MI and the use of health services can inform appropriate intervention strategies for these patients.

Kaiser Permanente adult patients with depression symptoms (Patient Health Questionnaire [PHQ-9] score > 5) seen in outpatient psychiatry (N = 302) who reported unhealthy alcohol use or other substance use (primarily cannabis) were randomized to three sessions of MI (intervention) or printed literature (control) with telephone follow-up interviews at 6 and 12 months. Cost-effectiveness analyses compared intervention costs associated with 30-day abstinence from unhealthy alcohol use (i.e., any days of ≥4/≥5 drinks for women/men) and cannabis use. Multivariable analyses examined associations between MI and healthcare utilization at 12 months (emergency department, primary care, psychiatry, and addiction treatment).

MI resulted in greater likelihood of abstaining from unhealthy alcohol use (70.0% vs. 60.2%, p < .01) and cannabis use (74.6% vs. 63.9%, p < .01) than the control at 6 months, but outcomes did not differ at 12 months. The 6-month incremental cost-effectiveness ratios were $1,207-$1,523 per abstinent patient for unhealthy drinking and $1,040-$1,313 per abstinent patient for cannabis. There were no differences between groups on health service utilization.

MI cost more than the control condition but yielded better outcomes at 6 months; MI had no relationship to health service utilization. Findings can inform implementation of substance use interventions through understanding MI's potential clinical and cost impact and its relationship to health services use.