Study on the relationship between medical cannabis laws and opioid analgesic overdose deaths


Bachhuber, M.A., et al. “Medical cannabis laws and opioid analgesic overdose mortality in the United States, 1999-2010.” JAMA Intern Med doi: 10.1001/jamainternmed.2014.4005. Published online August 25, 2014. 

The study, funded by NIH grants, was conducted by authors from Philadelphia VA Medical Center; University of Pennsylvania; Albert Einstein College of Medicine and Montefiore Medical Center, New York; and Johns Hopkins Bloomberg School of Public Health, Baltimore.

The objective was to determine the association between the presence of state medical cannabis laws and opioid analgesic overdose deaths.

Study methods

As of July 2014, 23 states had enacted laws establishing medical cannabis programs with chronic or severe pain as the primary indication for its medical use in most states.

Opioid analgesic overdose death rates in each state from 1999 to 2010 were obtained using the Online Data for Epidemiological Research interface to multiple cause-of-death data from the Centers for Disease Control and Prevention. Opioid analgesic overdose death was defined as fatal drug overdoses of any intent where an opioid analgesic was also involved. That captured all overdose deaths where an opioid analgesic was involved, including those involving polypharmacy and involving illicit drug use.

The study authors compared mean age-adjusted opioid analgesic overdose death rates for each year in states with medical cannabis programs during the study period 1999-2010 to overdose deaths rates in states with no cannabis laws.

Next, they determined the association between medical cannabis laws and opioid analgesic-related deaths using standard regression models. The depended variable was the analgesic overdose death rate. The main independent variable was the presence of medical cannabis laws. Two regression models were used: One included an indicator for the presence of a medical cannabis law in the state and year; the other allowed the effect of medical cannabis laws to vary depending on the time elapsed since enactment.

Several further analyses were performed using additional criteria. First, the authors excluded opioid deaths from suicide to focus exclusively on non-suicide deaths. Secondly, they included overdose deaths related to heroin, since heroin and prescription opioid use are interrelated for some individuals. Thirdly, they tested whether trends in opioid analgesic overdose mortality predated the implementation of medical cannabis laws by including indicator variables for the years before the passage of the law. Finally, they examined the association between medical cannabis laws and death rates of other medical conditions without strong links to cannabis use: heart disease and septicemia. This was to test the specificity of any association found between medical cannabis laws and opioid overdose deaths. 

Study results

  1. Medical cannabis laws were associated with a mean 24.8% lower annual rate of opioid analgesic overdose deaths compared with states without laws.
  2. In 2010, the lower rate of opioid analgesic overdose deaths translated to an estimated 1,729 fewer deaths than expected.
  3. The association between medical cannabis laws and opioid analgesia deaths was similar after excluding deaths by suicide and when including all heroin overdose deaths, even if an opioid analgesic was not involved.
  4. When examining the years prior to law implementation, the authors did not find an association between medical cannabis laws and opioid analgesic overdose deaths two years prior to law implementation or one year prior to law implementation. 
  5. The study did not find significant associations between medical cannabis laws and deaths due to heart disease or septicemia.

The association of medical cannabis laws with opioid analgesic overdose mortality in each year after implementation of laws in the U.S., 1999-2010

Year after law implementation

Mean lower annual rate of opioid analgesic overdose deaths













Discussion of study results

This study results suggested a link between medical cannabis laws and lower opioid analgesic overdose deaths.

The study found that, after analyzing death certificate data from 1999 to 2010, the states with medical cannabis laws had lower mean opioid analgesic overdose mortality rates compared with states without such laws. This finding persisted when excluding deaths by suicide, suggesting that medical cannabis laws were associated with lower opioid analgesic overdose mortality among individuals using opioid analgesics for medical indications.

In addition, the association between medical cannabis laws and lower opioid analgesic overdose death rates persisted when including all deaths related to heroin, even if no opioid analgesic was present, indicating that lower rates of opioid analgesic overdose deaths were no offset by higher rates of death due to heroin overdose.

According to the authors, evidence for the analgesic properties of cannabis is limited, but the drug may provide analgesia for some individuals. Patients already receiving opioid analgesics who start medical cannabis treatment may experience improved analgesia resulting in a decrease in their opioid dose. This would potentially decrease their dose-dependent risk of overdose. Also, if medical cannabis laws lead to decreases in the use of other drugs, particularly benzodiazepines, in people taking opioid analgesics, overdose risk would be decreased. 

Finally, although the study found a lower mean annual rate of opioid analgesic deaths is states with medical cannabis laws, the data dose not establish a direct causal link.

The report on prescribing medical marijuana and physicians’ quandary

Annas, G.J. “Medical  marijuana, physicians, and state law.” New England Journal of Medicine, September 11, 2014.

According to the author, Americans support making marijuana accessible to sick people who might benefit, and 86% of the public believe that doctors should be able to recommend marijuana to their seriously ill patients. However, federal law and the Drug Enforcement Agency (DEA) have consistently discouraged physicians from discussing marijuana with their patients. According to the author, the DEA apparently sees such discussions as legitimizing the use of a drug that was reasonably designated a Schedule I drug, with no medical use and a high potential for abuse.

The states that have adopted medical marijuana laws permit patients to possess marijuana on the advice of their physicians. State law however cannot change federal law, and the Department of Health and Human Services and the DEA used California as an example in 1996 to announce the intention to continue to enforce federal laws in California and to continue to review cases to determine whether to revoke the registration of any physician who recommends or prescribes Schedule I controlled substances.

Eventually, a trial court ruled that DEA action against a physician was permissible only if there was substantial evidence that the physician aided and abetted the purchase, cultivation or possession of marijuana as prohibited by federal law. In 2002, a circuit court of appeals affirmed the trial court ruling that the First Amendment prohibits government from punishing physicians on the basis of the content of doctor-patient communications.

However, once physicians move outside the doctor-patient relationship and into other arenas such as being medical officers or board members of marijuana dispensaries, the DEA seems to be treating them as drug dealers.

The author points out that since federal laws are unlikely to change, changes in state law become important.

It is likely more states will permit medical uses of marijuana. Special interest groups are presently advocating the federal government to repeal the ban on marijuana and leave regulation up to individual states. The author suggests that many special interest groups, including lawmakers and states’ rights proponents, will seek to protect physicians who follow their states’ medical-marijuana laws from overbearing and intimidating actions against them by the DEA. This may help to transform marijuana use from a criminal law issue to a medical issue.

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