6 in 10 Opioid Treatment Patients Used Cannabis, Most as a Harm Reduction Strategy | Research

The takeaway

Among 118 German opioid maintenance patients, 60% used cannabis, and 72% of those used it deliberately to reduce their intake of more dangerous drugs like heroin and benzodiazepines.

Addiction treatment providers, harm reduction advocates, opioid treatment researchers

72% of cannabis-using opioid patients used it to replace more dangerous drugs

What the researchers found

Sixty percent of opioid maintenance patients reported cannabis use. Of those, 72% used cannabis as a substitution strategy for other substances. Cannabis was most commonly used to replace heroin (44.8%) and benzodiazepines (16.4%). When asked to rate how well cannabis substituted for heroin (German school grades 1-6), the average was 2.6. Forty-seven percent used cannabis to reduce pain.

Why it matters

Rather than treating cannabis use in opioid patients as purely problematic, this study suggests many use it strategically as harm reduction, choosing a less dangerous substance over heroin or benzodiazepines.

The numbers in context

118 patients surveyed. 60% used cannabis. 72% of users employed it as substitution. Heroin substitution: 44.8%. Benzodiazepine substitution: 16.4%. Heroin substitution rated 2.6/6. Pain management: 47%.

How the study worked

Cross-sectional survey of 118 German opioid maintenance treatment patients using a questionnaire about cannabis use patterns, substitution motivations, self-medication purposes, and negative consequences.

What this study cannot tell us

Small single-center sample in Germany. Self-reported data. Cross-sectional design cannot confirm that cannabis actually reduced other drug use. No comparison group of non-cannabis-using patients.

How to read the evidence

Preliminary: small single-center cross-sectional survey with self-reported data

When this study was published

Published in 2025

The bigger picture

The harm reduction framing of cannabis use among opioid patients challenges the assumption that all concurrent substance use during treatment is negative. If cannabis helps patients reduce use of more lethal substances, it may have a net positive effect.

Questions still open

Does cannabis use actually improve opioid treatment outcomes? Should clinicians encourage or discourage this substitution strategy? Would formal cannabis-assisted treatment programs be more effective?

Common questions

Why do opioid patients use cannabis?

The most common reasons were to substitute for more dangerous drugs (especially heroin at 44.8% and benzodiazepines at 16.4%) and for pain management (47%). Most framed cannabis as a deliberate harm reduction strategy.

Does this mean cannabis should be part of opioid treatment?

This study suggests cannabis use in opioid patients is often strategic rather than random, but it cannot prove cannabis improves outcomes. The authors recommend viewing it as a potential harm reduction tool rather than automatically treating it as a problem.

Read the original research

Does cannabis use substitute for opioids? A preliminary exploratory survey in opioid maintenance patients.

European archives of psychiatry and clinical neuroscience, 275(2), 565-572

View on PubMed ↗Publisher’s paper ↗

Citation

Bekier, Nina Kim; Frischknecht, Ulrich; Eidenmueller, Katharina; Grimm, Franz; Bach, Patrick; Stenger, Manuel; Kiefer, Falk; Hermann, Derik. (2025). Does cannabis use substitute for opioids? A preliminary exploratory survey in opioid maintenance patients.. European archives of psychiatry and clinical neuroscience, 275(2), 565-572. https://doi.org/10.1007/s00406-023-01718-3