Cannabis doesn’t helps patients with opioid use disorder to stop using opioids


There has been interest in cannabis being used as a replacement drug for people with opioid use disorder, but research at McMaster University has found it doesn’t work.

The research team looked at all research on the effects of cannabis use on illicit opioid use during methadone maintenance therapy, which is a common treatment for opioid use disorder, and found six studies involving more than 3,600 participants.

However, a meta-analysis of the studies found cannabis use didn’t reduce illicit opioid use during treatment nor did it retain people in treatment.

The study was published today in the Canadian Medical Association Journal.

Cannabis use didn’t reduce illicit opioid use during treatment nor did it retain people in treatment.

“There is limited evidence that cannabis use may reduce opioid use in pain management, and some high-profile organizations have suggested cannabis is an ‘exit drug’ for illicit opioid use, but we found no evidence to suggest cannabis helps patients with opioid use disorder stop using opioids,” said senior author Dr. Zainab Samaan, associate professor of psychiatry and behavioural neurosciences at McMaster and a Hamilton staff psychiatrist.

Funding: The study was funded by the Canadian Institutes of Health Research.


Opioid use disorder (OUD) is a medical condition that is effectively treated with medications. A major challenge in breaking the cycle of OUD and related illegal activity is seamlessly introducing medications for opioid use disorder (MOUD) as individuals leave jail or prison. We examined the feasibility of a pilot intervention to link participants to ongoing MOUD and psychosocial supports following release from custody.


The study enrolled adults with a history of OUD released from Washington State prisons to Department of Corrections (DOC) community supervision. Participants were randomized to the study intervention or comparison group. The intervention consisted of education on OUD and available treatments, support with individualized treatment decision making, and continued care navigation for 6 months to facilitate linkage to chosen treatments. Participants randomized to the control condition received referral to services in the community from their community corrections officers. A care navigation activity log documented intervention participants’ intervention engagement, service utilization, and needs. Follow-up interviews were conducted at 1 and 6 months to assess satisfaction with the intervention.


Fifteen participants were enrolled. All were male, most were white (86.6%) and the average age was 36.9 years. The majority (14 of 15 participants) were near-daily heroin users with severe OUD prior to incarceration. Of the seven intervention participants, two wished to start medications immediately. Three participants reported starting buprenorphine or methadone in the subsequent follow-up period, with or without social support and/or outpatient counseling, and three reported enrolling in social support and/or outpatient counseling without medications. Participants who received the intervention reported high satisfaction. We discuss barriers and facilitators to study implementation.


An intervention to link participants to ongoing MOUD and psychosocial supports following release from prison had broad acceptability among participants and was feasible to implement among those recruited; however, enrollment was much lower than anticipated and the study intervention did not demonstrate the intended effect to facilitate use of MOUD immediately post-release in this small sample of participants.

Given recent research showing benefits of pre-release medication initiation, the potential added benefits of this two-part intervention should be studied in systems that initiate MOUD prior to release.


One-third of heroin users are incarcerated each year, primarily due to illegal activity related to their drug use. As such, there is an urgent need for interventions to facilitate initiation of effective treatments for opioid use disorder (OUD) upon release in order to break the cycle of relapse and re-incarceration.1 

The public health burden of OUD is relentless as the number of heroin and other illicit opioid users and the number having non-fatal and fatal opioid overdoses have increased significantly in recent years across the US, with pharmaceutical-type opioids serving as a common pathway into heroin and persistent overdose risk.26

The period immediately after release from prison is one of greatly increased risk for fatal opioid overdose.7,8 Opioid use disorder can be readily treated with agonist medications for opioid use disorder (MOUD), methadone and buprenorphine, reducing illegal activity and recidivism, improving functioning, decreasing mortality and transmission of infectious diseases like HIV and HCV, and substantially reducing costs.916 Long-acting naltrexone, an opioid antagonist, is a newer medication for OUD and data demonstrate effectiveness for reducing opioid use, but challenges with initiation and retention.1720 

A major challenge in breaking the cycle of OUD and illegal behaviors, and related morbidity and mortality, is seamlessly getting individuals on MOUD as they leave jail or prison. This process may be enhanced by simultaneously building interest in effective treatments among newly released inmates and facilitating access to such treatments. Given the very challenging psychosocial environments into which people are released and the high risk of relapse, initiating medications quickly is vital.1,7,21

Washington State’s Opioid Response Plan identifies numerous challenges to providing effective services to people being released from prison with OUD, including:

1) identification of the population at risk,

2) inmates’ often modest knowledge and misperceptions of MOUD as well as limited motivation and self-efficacy for accessing treatment,

3) lack of continuity of care between the relatively protected prison environment and effective services in the community, and

4) maintaining ongoing utilization of MOUD to support recovery and reduced consequences related to opioid use.22

Given the many gaps and barriers for people post-prison release, we developed a two-part intervention. The first part of the intervention was treatment decision making adapted from the shared decision making approach often used in health care which we adapted to OUD, moved out of the clinical setting, and had delivered by non-health care providers.23,24 

In order to increase the chances of a person initiating, and due to the likelihood of needing to re-initiate care, we also provided 6 months of ongoing treatment navigation services.21

 A pilot feasibility randomized controlled trial was chosen to examine the feasibility of the research procedures and the study intervention.

McMaster University
Media Contacts:
Veronica McGuire – McMaster University
Image Source:
The image is in the public domain.

Original Research: Closed access
“Cannabis use during methadone maintenance treatment for opioid use disorder: a systematic review and meta-analysis”. Zainab Samaan et al.
Canadian Medical Association Journal doi:10.9778/cmajo.20190026.


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