Evidence-based therapist guided introduction to online heavy cannabis use treatment in Canadian adults: a Randomized Controlled Trial (RCT)

TL;DR

A Canadian study tested an online cannabis use treatment program with therapist support and found it reduced cannabis use and related problems.

Contribution

This study evaluates a new Canadian version of the CANreduce program with MET-informed therapist guidance for heavy cannabis users.

Findings

All participants reduced cannabis use frequency and related problems by the end of treatment and follow-up.

MET-therapist guidance led to greater reductions in cannabis quantity used compared to a waitlist control.

The non-MET research assistant condition showed significant reductions in cannabis problems compared to the control.

Abstract

Many people who engage in heavy cannabis use do not seek treatment, and those who do are often met with long treatment wait times or high cost of services. Online treatment programs reduce barriers to accessing treatment in a timely manner. Online cannabis use treatment programs are effective, showing moderate effect sizes, particularly with text-based therapist support. Literature suggests brief therapist-guided introductions (i.e., self-completed interventions offered with the support of a therapist) informed by Motivational Enhancement Therapy (MET) may help to bolster and maintain program gains. The current evaluation of MET-informed therapist-guided introduction was conducted with a sample of Canadians who report heavy cannabis use, using a new Canadian version of CANreduce, an online treatment program for heavy cannabis use.

The intervention was pre-registered on clinicaltrials.gov for traceability (ID: NCT04965012). Participants (N = 152) were randomized into one of three conditions: MET-therapist guided introduction plus 6-week, online, self-guided treatment program; non-MET research assistant introduction plus 6-week, online, self-guided treatment program; or a psychoeducational control condition. Module content to reduce cannabis use was informed by cognitive behavioural therapy and motivational interviewing approaches. Participants completed assessments at baseline, end of treatment (i.e., 6 weeks), and at follow up (i.e., 10 weeks). Data were analyzed using Generalized Estimating Equations.

All participants reduced their cannabis consumption frequency (use days in the past week), as well as cannabis-related problems, at end of treatment and follow up. Participants in the MET-therapist condition showed significantly greater reductions in quantity of cannabis used over time compared to the waitlist control. Participants in the non-MET research assistant condition showed significantly greater reductions in cannabis problems compared to waitlist control. There were no significant differences between MET-therapist guided conditions and non-MET research assistant conditions. There was no significant effect of condition on cannabis consumption days in the past week, anxiety, depression or quality of life.

The present study provides preliminary support for the CANreduce program in addition to the MET-therapist guided introduction.

The online version contains supplementary material available at 10.1186/s42238-025-00378-5.

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