Is there an association between the use of cannabis and the nonmedical use of prescription opiates? This is an important question in light of the increasing legal availability of marijuana. Some people have raised the possibility that medical marijuana may help some individuals manage severe pain and decrease opiate use. However, there are few prospective studies investigating the relationship of cannabis use and subsequent nonmedical use of prescription opiates.
Mark Olfson and colleagues address this issue in a recent paper in the American Journal of Psychiatry. Using data from NESARC (the National Epidemiological Survey on Alcohol and Related Conditions), the authors examined the association between cannabis use reported in the 2001-2002 survey and nonmedical use of prescription opiates 3 years later. Nonmedical use of a prescription opiate was defined as using the drug “without a prescription, in greater amounts, more often, or longer than prescribed, or for a reason other than a doctor said you should use them” during the previous 12 months.
The major conclusion from the analysis conducted by the Olfson group was quite clear: people who used cannabis in the 12-month period prior to the initial interview were at increased risk of nonmedical use of prescription opiates 3 years later. This was true even when the data were adjusted to control for age, sex, race/ethnicity, family history variables, antisocial personality disorder, other substance use disorders, and mood or anxiety disorders. Furthermore, the percentage of people with incident prescription opioid use disorder at the second interview increased as the level of cannabis use reported at the first interview increased. (Incident prescription opioid use disorder was defined as use that occurred since the first interview that meets criteria for opioid use disorder, restricted to people who had no prior lifetime history of opioid use disorder.)
Interestingly, there have been some reports that death rates from opiate overdose are lower and prescriptions for opiates reduced in states with medical marijuana laws. Yet, Olfson and colleagues report a 5 to 9-fold increase in nonmedical prescription opiate use in those who used marijuana. Further research will be needed to elucidate the effect of medical marijuana laws on prescription opiate use and misuse.
The association of marijuana use and nonmedical prescription opiate use 3 years later does not necessarily mean that marijuana use causes increased opiate use. However, based on animal studies, it is possible that cannabis use can lead to brain changes that make individuals more susceptible to opiate misuse. In addition to the direct effects of marijuana on the brain, marijuana use may lead to non-biological factors that increase the risk of using opiates. For example, individuals who regularly use marijuana may interact more often with people who have access to opiates.
The authors acknowledge that the majority of adults who use cannabis do not start or increase use of prescription opiates. However, they do suggest the possibility that increased marijuana use may be contributing to the current opiate crisis.
As marijuana becomes increasingly available for both medical and recreational use, more research is essential to examine direct and indirect relationships between marijuana use and opiate misuse.
Olfson, M., Wall, M.M., Liu, S.-M., & Blanco, C. (2018). Cannabis use and risk of prescription opioid use disorder in the United States. Am J Psychiatry. 175:47-53.