Advocates are claiming medical marijuana can help to fight the opioid epidemic but data show the opposite. Rather than being at lower risk, people who use medical marijuana may be at higher risk for non-medical prescription drug use.
Much of medical marijuana usage was always recreational and a new study in the Journal of Addiction Medicine finds that people who use medical marijuana have higher rates of prescription drug use - including pain relievers.

Does Use of Medical Marijuana Increase or Decrease Prescription Drug Use?

The researchers analyzed more than 57,000 responses to the 2015 National Survey on Drug Use and Health. Participants were asked about medical and non-medical ("inconsistent with doctor's instructions") use of prescription drugs. The survey also asked about marijuana use, including whether it was recommended by a healthcare professional. The survey identified 776 people who used medical marijuana--about 1.4 percent of all responders.

People who used medical marijuana were more likely to say they had used prescription drugs in the past year. They were about 60 percent more likely to report any prescription drug use, relative to those who did not use medical marijuana.

People who used medical marijuana were also more than twice as likely to report non-medical use of prescription drugs, including pain relievers, stimulants, and tranquilizers.

Higher levels of non-medical prescription drug use by people who used medical marijuana persisted in an analysis limited to people who used prescription drugs. The researchers write, "This suggests that the elevated risk for prescription drug non-medical use among people who use medical marijuana cannot be ascribed simply to their having a medical concern or greater access to prescription drugs."

Previous studies have reported that states where medical marijuana is legal have lower rates of medical and non-medical prescription drug use and related harms--including opioid overdose. 

Like all sociological studies, be they related to issues like marijuana and drug use or gun violence or surveys about vaping in teens, other factors may explain the association.   There is also a lack of large-scale follow-up data on whether patients are using cannabis together with or in place of prescription drugs.