We can’t claim that marijuana is a treatment for opioid addiction without proper evidence

An increasingly common question has been whether marijuana constitutes such treatment. Some states have been reviewing petitions to allow medical marijuana as a treatment for opioid addiction, including the state of Connecticut. 

But what do we know about using marijuana to treat opioid addiction?

Opioid addiction is baffling because it doesn’t respond well to many treatments that seem intuitive. However, it does respond to agonist treatment with buprenorphine and methadone, and to injectable naltrexone.  

{mosads}Given what we know about opioid addiction and the treatments that work for it, it is not clear how marijuana would exert a therapeutic effect. 

Some posit that its possible pain relieving properties would lower opioid use. Yet, pain is not a symptom of opioid addiction, where compulsive use is driven not by inadequate pain control, but by the addiction itself.

A related argument that the availability of marijuana for pain relief would lower opioid use in general, ought to direct the conversation toward the potential role of medical marijuana in the treatment of pain, rather than in opioid addiction. And even for that the evidence is limited, and findings from large epidemiological data have not found an association between cannabis use and lower opioid doses among people with pain.

Others argue that the relatively safer psychoactive effects of marijuana may be satisfying enough to deter from opioids use. But psychoactive effects do not replace one another in this manner and the deep hold opioids have on the brain in opioid addiction makes this exceedingly unlikely. Furthermore, research does not support the belief that people substitute one addiction for another. 

Preclinical animal models and a pilot study in humans suggest a potential future role for the cannabinoid cannabidiol in reducing cue-induced anxiety and craving for heroin. 

In a recent article, the lead researcher of the pilot human investigation stressed that, while the results are promising, they are not sufficient to draw sweeping conclusions on its use in treating opioid addiction. 

She also states that tetrahydrocannabinol, which is the main psychoactive cannabinoid in marijuana, is not a suitable option because it has the potential to induce substance use and cause other mental health problems.

Moreover, we do have further data to inform us. In a prospective study, cannabis use after discharge from inpatient treatment increased the risk of relapse to alcohol and cocaine, but had no effect on heroin outcomes. 

A recent retrospective cohort study found that cannabis use predicted dropping out of opioid agonist treatment. The authors conclude that, despite the possibly positive effects of marijuana legalization for the general population, patients receiving opioid agonist therapy may be negatively impacted. 

These findings are not conclusive, and other research did not find an association between cannabis use and retention or use of heroin or cocaine during agonist treatment. Furthermore, an observational study demonstrated favorable outcomes for intermittent use of marijuana, cocaine, and benzodiazepines during treatment with oral naltrexone for opioid use disorder. 

The findings were replicated in a study showing an association between intermittent marijuana use and retention in treatment with oral naltrexone, whereas abstinence and heavy use were associated with high rates of dropping out. 

In this study, most of the effect occurred in the first month after detoxification, indicating a possible role of marijuana in alleviating continued withdrawal symptoms that may have been, in part, due to the antagonist effects of naltrexone. (Of note, evidence does not support the use of oral naltrexone as a viable treatment for opioid use disorder).

Overall, while less dangerous than opioids by far, and possibly helpful for some conditions, including pain, no findings, to my knowledge, clearly demonstrate that marijuana use positively impacts people with opioid use disorder. Moreover, marijuana use carries risks, including cannabis use disorder, psychosis and cognitive impairment, as well as additive effects when used with other substances, including opioids.

Withdrawal is a somewhat different matter. It is plausible that marijuana may modestly ease withdrawal symptoms, and clinical findings support this. However, not only are there more effective ways of managing opioid withdrawal, but detoxification off opioids altogether is not recommended for most people with opioid addiction. Rather, agonist treatment with buprenorphine or methadone is considered to be first-line, and is often undermined by tactics that highlight detoxification as treatment.

Ecological studies add another dimension. One study demonstrated a lower rate of opioid overdose deaths in states that have implemented medical marijuana laws, but it did not find a clear connection between such laws and the rates of opioid overdose deaths among those with opioid use disorder. Another analysis reported a relative decrease in opioid overdose deaths in states that permit medical marijuana dispensaries. 

Yet drawing inferences about causality is impossible from such data, including the specific impact on individuals with opioid use disorder. A recent study using epidemiologic data found a strong prospective association between cannabis use and subsequent opioid use and opioid use disorder. The authors raise the possibility that “the recent increase in cannabis use may have worsened the opioid crisis.”

Unfortunately, there are no large randomized controlled trials to guide us — not to mention that marijuana research is hampered by federal regulations. 

And medical marijuana may have benefits that are not captured by studies of illicit marijuana use. Nonetheless, it is misguided to claim without credible evidence that marijuana is a treatment for opioid addiction. 

Marijuana ought to be subjected to the same rigorous approval process that we apply to other pharmacologic agents, which also means that specific putative compounds should be isolated and studied. And it may well be that recreational marijuana ought to be legalized, but the use of medical marijuana as a half-measure on that path is problematic, especially in conditions for which there is no solid evidence of its net benefit.

Where does this leave us? At this point stronger evidence supports the potentially deleterious effects of marijuana in opioid use disorder, rather than its utility in its treatment. 

We do have effective treatments for opioid addiction that are not being adequately accessed; meanwhile, giving false hope to patients and their families by steering them toward unproven, risky measures is unethical and potentially dangerous.