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.
Concern about medical cannabis legalization leading to teens feeling encouraged to use the plant recreationally and more frequently has been widely expressed. However, a recent study published in The Lancet Psychiatry concluded there are no significant links between adolescent cannabis use and the legalization of medical marijuana.
The comprehensive study, “Medical marijuana laws and adolescent marijuana use in the USA from 1991 to 2014: results from annual, repeated cross-sectional surveys,” spanned a period of 24 years from 1991 though 2014. Over one million teens from the ages of 13 to 18 completed the government-funded survey. Given to 8th, 10th and 12th graders in 48 states, the periodic questionnaire focused on cannabis consumption in the previous month.
While it is important to note that teen cannabis use was generally higher in states that went on to legalize medical consumption, researchers did not see an additional spike in the plant’s usage after laws were passed. In fact, overall use by 8th graders decreased in states with legal medical marijuana. Some scientists speculated that the fall was due to children viewing the now ‘adult-approved’ plant to be less of an enjoyable recreational activity. Others considered that parents might be working harder to stop their children from trying cannabis.
Deborah Hasin, a reviewer of the data and Professor of Epidemiology at Columbia University Medical Center in New York stated:
“Our findings provide the strongest evidence to date that marijuana use by teenagers does not increase after a state legalizes medical marijuana.”
However, this is not the only report or study that points to this conclusion. In 2013, the Colorado Department of Health and Environment showed that high school cannabis consumption decreased from 22 percent to 20 percent over the course of 2011 to 2013. Dr. Larry Wolk, CDPHE’s director, suggested that as with tobacco, youth prevention campaigns likely ensure that adult legalization does not impact the health of the state’s children.
The 13th Biennial California Student Survey found that marijuana consumption in teens was less than in years before medical cannabis was legal. The researchers also noted that the plant’s usage increased in states where medical marijuana was prohibited.
Dr. Kevin Hill from McLean Hospital’s Division of Alcohol and Drug Abuse said of Hasin’s most recent study:
“Future decisions that states make about whether or not to enact medical marijuana laws should be at least partly guided by this evidence. The framework of using a scientific method to challenge what might be ideological beliefs must remain an important driver of future research on marijuana policy.”
Harvard Univeristy’s 2014 Harvard Public Opinion Project, found that legalization does not encourage marijuana use. This study focused on full legalization rather than solely on medical marijuana legalization. Nearly 90 percent of participants who have not used marijuana responded that they are not likely to change behavior if it is legalized.
Why has teen cannabis use decreased as a result of legalization? Although one exact answer is not yet known, it may have something to do with increased knowledge about cannabis. The answer to this question is a complicated and multifaceted one that will require more study. However, this most recent research signals a new wave of understanding for this fascinating plant.