Coming Off Opioids with Cannabis: List of Studies

Written by

Lee Johnson

Lee Johnson is the senior editor at CBD Oracle, and has been covering science, vaping and cannabis for over 10 years. He has a MS in Theoretical Physics from Uppsala...

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Cannabis and opioids
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With medical uses of cannabis being accepted by the majority of states, and the potential uses increasing the more scientists research various cannabinoids, some promising avenues might seem quite surprising at first. One of these more unexpected potential uses flies right in the face of the way many people think about cannabis: there are several studies that suggest that cannabis – CBD in particular – could be useful for people struggling with addiction to opioids, whether prescription pills or heroin.

As with many areas of cannabis research, there aren’t tons of studies yet, but there are enough that approach the issue from different perspectives to give us reason to suspect that weed really could help people come off opioids.

At a Glance:

  • 50,000 Americans died of opioid overdose in 2019 (close to 100,000 in 2020)
  • People taking opioids who use either cannabis or just CBD often start taking less opioids (in one study, 55% reduced and 26% stopped altogether), and are less likely to relapse.
  • People in treatment for opioid addiction who use cannabis tend to stay in treatment for longer, although studies disagree whether this is for daily or intermittent use.
  • CBD reduces cravings and anxiety during withdrawal, and THC also reduces withdrawal symptoms.
  • States with medical marijuana programs prescribe fewer opioids.

The Opioid Crisis Explained

Opioid painkillers are in the same chemical family as heroin, but with the intention that they’ll be used for a short period of time in reasonable doses to treat severe pain. Once you go past acetaminophen and ibuprofen, there aren’t many options for pain management other than opioids, but doctors were understandably unsure about prescribing them unless it was absolutely needed.

However, in the late 90s, the pharmaceutical industry went to some effort to reformulate drugs like oxycodone in “slow release” form, but more importantly marketed and lobbied to encourage prescriptions for a wider range of conditions. A key part of this strategy was convincing doctors that the new formulations didn’t have much potential for addiction.

Opioid overdose deaths in the U.S. between 1999-2019
National drug overdose deaths involving any opioid. Source: National Institute on Drug Abuse

But they do. As prescriptions increased, so did addiction and death. By 2019, about 50,000 Americans died from overdoses involving opioids, around a quarter of people they’re prescribed to end up misusing them, and one in 10 ends up addicted. Lawmakers tried to get on top of the problem in the 2010s especially, but then already-addicted patients often just switched over to heroin, and now 80% of heroin users started with prescription pills. While some effective but less dangerous pain relievers would be great – and cannabis is a candidate for that too – finding some way to tackle this addiction crisis is an understandable priority.

The Studies

There are a lot of studies looking generally at the relationship between cannabis and opioid use, but here are some of the most important ones for the question of whether weed can help people come off opioids.

Medical Cannabis Helps Opioid Users Quit or Reduce Their Use

A Pilot Study of a Medical Cannabis – Opioid Reduction Program (2019)

Original study ›

What They Did

This Canadian study is more a “proof of concept” than anything concrete, but it does prove the concept pretty well.

The research involved 600 patients taking opioids every day, across a wide range of dosages, all of whom wanted to reduce their dosage.

They were all given access to an online mental health and wellness tool, and 0.5g of medical cannabis a day for every 10% reduction in their opioid dose, but this was intended to be used as needed so they varied it through the course of the study.

They worked with the patients for six months and they had regular check-ups with doctors to change things as needed.

What They Found

After six months, 26% of the group had stopped taking opioids altogether, another 55% had reduced their use of opioids (by an average of about a third) and the remaining 19% showed no change.

Only one of the patients increased their use, but the condition was severe and the pain wasn’t being managed well initially. Of course, with no comparison group not using cannabis and the group also receiving psychological support, it’s difficult to come to any firm conclusions on the basis of this alone, but it does clearly show that it’s feasible to introduce cannabis into opioid treatment regimen with no apparent ill effects.

Cannabidiol as a Treatment for Addiction

Early Phase in the Development of Cannabidiol as a Treatment for Addiction: Opioid Relapse Takes Initial Center Stage (2015)

Original paper ›

An Overview

This paper is a little different in that it’s not original research as much as a review and primer on the science of why cannabis might help with opioid addiction from a biochemistry perspective, and looking at the early-stage research that had been conducted up until its publication in 2015.

In particular, the research singles CBD (i.e. cannabidiol) out as the cannabinoid to focus on, largely due to its anxiety-relieving qualities and the fact that it’s not psychoactive or potentially addictive in itself.

The researchers point out that while CBD hadn’t been investigated enough for addiction to different substances (other than opioids) or at many stages of the addiction cycle, there is still a lot of potential.

In particular, they write that the early-stage evidence “collectively sets a strong foundation in support of the further exploration of CBD as a therapeutic intervention against opioid relapse.” Of course, there has been a lot more research conducted since this paper came out, but the whole paper is free and it provides a detailed – if a little hard to read in places – introduction to the issue and the evidence.

CBD Reduces Opioid Use and Improves Quality of Life

Evaluation of the effects of CBD hemp extract on opioid use and quality of life indicators in chronic pain patients: a prospective cohort study (2019)

Original study ›

What They Did

This study is another one that’s more of a proof of concept than a controlled study, but the researchers set out to see the effect of full hemp extract CBD (i.e. with CBD, other cannabinoids and terpenes but only trace amounts of THC) on opioid use and pain in a group of participants from a pain management center who were taking opioids.

The study ran for eight weeks, and 97 participants (who had all been using opioids for at least a year) continued through to the end. Most of the participants used 30mg of CBD per day, with one using 60mg and another two just using 15mg.

What They Found

The results showed that 53% of the pain patients reduced their opioid use by the end of the eight-week period, but none of the three who chose not to use CBD reduced their use.

On top of this, 94% of those using CBD said their quality of life improved, and there was a significant relationship between CBD use and improvement on a sleep quality index and the pain intensity and interference test.

Although the change wasn’t significant, there was also a trend towards improvement on the patient health questionnaire and the pain disability index for the CBD users. Overall this is another positive result but one limited by the non-controlled nature of the research.

People Who Use Cannabis are Less Likely to Relapse

Cannabis use is associated with reduced risk of exposure to fentanyl among people on opioid agonist therapy during a community-wide overdose crisis (2020)

Original study ›

What They Did

This study used data from two groups of people who used drugs in Vancouver, who were on opioid agonist therapy (e.g. taking methadone), and aimed to investigate the relationship between cannabis use and fentanyl use.

They chose to focus on fentanyl because it’s one of the most important substances in terms of perpetuating the opioid crisis. The research was conducted between 2016 and 2018, with a total of 819 participants included.

What They Found

They found that while most of the participants used fentanyl overall (53%), people who tested positive for THC were significantly less likely to use it, with 47% of cannabis users taking fentanyl vs. 56% of those who tested negative.

This significant difference persisted throughout the entire study. It’s important to note that this was “self-selected” (i.e. those who used cannabis did so because they wanted to), but regardless, it’s a good sign for the impact of cannabis on opioid use.

The researchers conclude “Our findings reinforce the need for experimental trials to investigate the potential benefits and risks of controlled cannabinoid administration for people on opioid agonist therapy.”

Daily Cannabis Users Are More Likely to Stay in Opioid Treatment

High-intensity cannabis use is associated with retention in opioid agonist treatment: a longitudinal analysis (2018)

Original study ›

What They Did

This study is an earlier data-set from the same group who studied the relationship between cannabis use and fentanyl in Canada above, and again uses data from people who use drugs in Vancouver.

However, this study focuses on opioids more generally, and in particular whether they stay on the opioid agonist treatment program, which they defined as remaining in the program for two consecutive six-month periods.

They had a total of 820 participants, and followed up with them for a median of 81 months. About 18% of the group used cannabis at least daily, and these were compared to people who used cannabis less than daily.

What They Found

The results showed that people who used cannabis at least daily were 21% more likely to be retained in treatment, compared to less than daily users.

They conducted an additional analysis to compare daily users and less than daily users to non-users, and this showed that daily users were more likely to be retained in treatment than people who don’t use cannabis, whereas less frequent users showed no difference.

Daily Cannabis Use is Better Than Intermittent for Avoiding Relapse

The association between cannabis use and outcome in pharmacological treatment for opioid use disorder (2021)

Original study ›

What They Did

This study looked at the impact of cannabis use on opioid addiction, with sizable groups of both cannabis users and non-users to make comparisons more robust.

They recruited 2,315 people who were receiving psychological treatment for their opioid use, and then asked them about their cannabis use over the past month. They followed up with the participants for three months, tracking their use of opioids through urine testing and asking questions to determine how often they used cannabis.

What They Found

Overall, 51% of the participants used cannabis. Overall, using cannabis with any frequency had no impact on how much they took opioids compared to the non-users.

They did find some differences between people who used cannabis in differing amounts, though, with the daily users (almost 70% of those who did) being less likely to use opioids than those who only used occasionally.

People who started using cannabis at an older age were also less likely to use opioids, compared to those who started younger. Generally, 75% of the cannabis users said that it didn’t affect their treatment either positively or negatively.

The overall findings of this study don’t really point to cannabis being useful, but the authors do point out that the variation based on how often they used cannabis is worth investigating further.

CBD Reduces Craving and Anxiety During Opioid Withdrawal

Cannabidiol for the Reduction of Cue-Induced Craving and Anxiety in Drug-Abstinent Individuals With Heroin Use Disorder: A Double-Blind Randomized Placebo-Controlled Trial (2019)

Original study ›

What They Did

This study is a double-blind, placebo-controlled trial that focused on the impact of CBD on cue-induced craving and anxiety in people with heroin use disorder.

This basically means the individuals’ response to cues such as videos of people injecting or snorting drugs (based on how the participant preferred to use) and to being shown heroin paraphernalia (e.g. a syringe or a powder that looks like heroin), which is an important factor that leads people to relapse.

The test involved 42 participants, who were randomly assigned to receive either placebo, 400mg or 800mg of CBD each day for three days. They were assessed throughout the days taking the CBD and seven days after the last dose.

What They Found

The results showed that the CBD reduced both cravings and anxiety in response to the drug-associated vs. negative cues both on the day of administration and seven days later, compared to the placebo.

It also reduced physical responses such as increases in heart rate or production of cortisol (the “stress hormone”). The researchers said the results provide a “strong basis” for further investigation of CBD as a way to help people manage heroin withdrawal and maintain abstinence.

THC Reduces Opioid Withdrawal Symptoms

The effects of dronabinol during detoxification and the initiation of treatment with extended release naltrexone (2015)

Original study ›

What They Did

This double-blind, placebo controlled study looked at the effect of receiving dronabinol (THC, brand name Marinol) during the process of detoxification and treatment for opioid dependence.

All 60 participants were given naltrexone (which reduces the effects of opioids), and 40 received dronabinol while the other 20 received placebo during the detox process and for 5 weeks afterwards. The whole trial lasted for 8 weeks, and the researchers were mainly interested in the impact of this on a patient-rated scale of opioid withdrawal symptoms.

What They Found

Overall, they found that the patients who received dronabinol had significantly less severe withdrawal symptoms compared to those who got the placebo.

Both groups were equally likely to complete treatment, though. However, additional analyses showed that the patients who also smoked cannabis regularly after detoxification reported less insomnia and anxiety, and were more likely to complete the trial (although these could be from either group).

Intermittent Cannabis Users Stay in Opioid Treatment for Longer

Intermittent Marijuana Use Is Associated with Improved Retention in Naltrexone Treatment for Opiate-Dependence (2009)

Original study ›

What They Did

This study looked at the effect of different intensities of cannabis use on people staying on naltrexone treatment for opioid addiction.

The 63 patients included in the study were randomized to either receive six months of genuine behavioral therapy or a control behavioral therapy – in addition to the naltrexone – and researchers classified them into non-users, intermittent users and consistent users of cannabis on the basis of drug tests conducted as part of the research (with 80% positive or more being classed as consistent).

What They Found

The results showed that people who used cannabis intermittently – but not non-users or consistent users – stayed on naltrexone treatment for longer, with a median of 133 days vs. 35 for both non-users and consistent users.

They adjusted for relevant factors, such as how much heroin they were using at the start of treatment and whether they used cocaine during treatment, and the results from the basic analysis remained unchanged. In short, the study seems to show that intermittent cannabis use is the best approach for people looking to stick with naltrexone treatment.

States with Medical Cannabis Programs Prescribe Fewer Opioids

State Medical Cannabis Laws Associated With Reduction in Opioid Prescriptions by Orthopaedic Surgeons in Medicare Part D Cohort (2021)

Original study ›

What They Did

This study is quite different from all the others, in that it investigates the issue in a bit of a non-direct way. In particular, it looks at the difference in opioid prescriptions between states with a medical cannabis law and those without one.

They used the Medicare Part D database to track daily doses of opioid medications – including hydrocodone, oxycodone, fentanyl, morphine, methadone and others – and statistically analyzed this in combination with information about the state’s medical cannabis laws.

What They Found

The results showed that states with legalized medical cannabis prescribed fewer doses of opioids than those without such programs. Overall, states with a medical cannabis law showed a 19.7% reduction in doses prescribed annually, and those with in-state dispensaries had a 13.1% reduction in prescribing. 

They didn’t find a link between legalized marijuana and prescribing, though. There are many other studies that look at this same basic issue and come to similar conclusions, too.


This article doesn’t cover everything, but a substantial amount of the human research that has been conducted is covered here. The picture – as always – is complicated. There are many reasons to think that cannabis could play a role in helping with the opioid crisis, whether through providing an alternative source of pain relief (resulting in fewer prescriptions) or by actively helping people overcome addiction or get through withdrawal.

However, the studies conducted so far are either limited by design (for instance, no control group for comparisons) or by size (most of the better studies only have around 50 participants). That said, with more research being conducted all the time, it’s likely that we’ll pin down the role THC and CBD can play in helping with opioid addictions in the next five to ten years.

Related: The most impactful studies on cannabis