A new study published in JAMA Psychiatry shows a connection between medical marijuana and illegal use, and sometimes overuse.
Results from the study conclude that between 1991-1992, illicit use in states without medical marijuana was at 4.54 percent. By 2012-2013, illicit use was at 6.7 percent. During those same time periods in states with legal medical marijuana, illicit use was at 5.55 percent and then 9.15 percent.
Cannabis use disorder also increased during these times. Between 1991-1992, use disorder occurred in states without medical marijuana legislation at a rate of 1.35 percent, compared to a rate of 3.1 percent between 2012-2013.
Overall, states with medical marijuana legislation had an increase in illicit use of 1.43 percentage points, compared to .66 in states without medical marijuana laws.
The study defined the “illicit use” of cannabis as consumption on 12 or more occasions within the previous year, without a doctor’s supervision. The study also considers cannabis use disorder as having a negative impact on a person’s well-being, with symptoms like cravings.
“If you increase the prevalence of users, you are going to increase the prevalence of people who have adverse consequences,”
said lead author Deborah Hasin, a professor of epidemiology at Columbia University’s Mailman School of Public Health, and lead author of the study.
Hasin says the data is important when lawmakers are weighing decisions on marijuana policy. “Just as the case for alcohol, not everybody who uses it is harmed but there are some risks,” Hasin said to Reuters Health.
The results of Hasin’s study could be skewed. The data was based on in-person interviews rather than an anonymous method of data-collecting, some of which were conducted by government employees. In addition, the data was gathered from three studies conducted between 1991-2013. California didn’t legalize medical marijuana until 1996. This calls into question how candid participants were when answering questions, the majority of which were asked before normalization and legalization had begun in earnest.
“This researcher seems to be intent on showing some increase in marijuana use disorders, and yet every other researcher has come up with the exact opposite conclusion,” said Mason Tvert of Marijuana Policy Project. “This research is contradicted by years of data and every other study that’s been done on this subject.”
He also views the study’s definition of abuse as beginning at once-a-month consumption, a definition that would label 80 percent of Americans as alcoholics.
Using the date range in the study, the number of Americans who lived in states with legal medical marijuana went from zero in 1991 to 103,994,437 in 2013, based on census data from 2013 and the states that had legalized medical marijuana by that year.