Legal medical marijuana may be reducing the number of people abusing opioids, according to a new study at Columbia University’s Mailman School of Public Health.
In order to investigate the link between state medical marijuana laws and opioid use, the researchers analyzed fatal car crash data in states that test for drug use if the driver dies within one hour of the accident. The findings show that there were fewer drivers killed in car crashes who tested positive for opioids in states with medical marijuana laws than before the laws went into effect.
“We would expect the adverse consequences of opioid use to decrease over time in states where medical marijuana use is legal, as individuals substitute marijuana for opioids in the treatment of severe or chronic pain,” said lead author June H. Kim, M.Phil., a doctoral student in the Department of Epidemiology at the Mailman School of Public Health.
For the study, the researchers looked at data from the 1999-2013 Fatality Analysis Reporting System from 18 U.S. states that tested for alcohol and other drugs in at least 80 percent of drivers who died within one hour of crashing.
The researchers looked for opioid positivity in drivers ages 21 to 40 who crashed their cars in states with an operational medical marijuana law compared with drivers who crashed in states before those laws went into effect. The findings show an overall reduction in opioid positivity for most states after an operational medical marijuana law began.
In 1996, California was the first state to pass a voter-initiated medical marijuana law. Since then, 22 additional states and the District of Columbia have enacted their own medical marijuana laws either by voter initiatives or through state legislation.
“The trend may have been particularly strong among the age group surveyed because minimum age requirements restrict access to medical marijuana to patients age 21 and older, and most medical marijuana patients are younger than 45,” said Kim.
The authors say they would expect to see similar reductions in opioid use among older cohorts if medical marijuana is increasingly embraced by older generations.
“This study is about the possible substitution relationship between marijuana and opioids. The toxicological testing data for fatally injured drivers lend some suggestive evidence that supports the substitution hypothesis in young adults, but not in older adults,” said senior author Guohua Li, M.D., Dr.P.H.
“As states with these laws move toward legalizing marijuana more broadly for recreational purposes, future studies are needed to assess the impact these laws may have on opioid use,” said Kim, professor of epidemiology and founding director of the Center for Injury Epidemiology and Prevention at Columbia..
The findings are published online in the American Journal of Public Health.