A new study published in the medical journal JAMA Pediatrics, involving data from 1.4 million U.S. high school students and claiming to be the most credible analysis to date, has shown evidence that the rate of youth cannabis use in recreationally legal states is falling.
“Because our study is based on more policy variation than prior work, we view our estimates as the most credible to date in the literature,” said the paper’s lead author D. Mark Anderson, an associate professor at Montana State University whose work focuses on health economics, risky behavior, and crime.
Taking data from the U.S. Centers for Disease Control and Prevention’s (CDC) annual national Youth Risk Behavior Survey from 1993 to 2017, Anderson’s study found that legalized recreational cannabis was responsible for an 8 percent drop in past-month high school users, and a 9 percent drop in heavy users who self-reported 10 uses or more in the past 30 days.
Anderson’s study found that medical cannabis legalization has no effect on teen use, diverging from another 2019 report that drew on a smaller window of the same Youth Risk Behavior Survey data and found a slight decrease in teen use in states with legal medical cannabis. That study was led by Rebekah Levine Coley, chair of counseling, developmental and educational psychology at Boston College’s Lynch School of Education and Human Development, and found a 1.1 percent reduction in the number of high school students self-reporting past-month cannabis use from 1999 to 2015.
Other studies have found similar trends of decreased teen use in legal cannabis states, amid a background of national teen cannabis use that has fallen to its lowest level in the past 20 years while the overall base of American cannabis users continues to rise.
But not everyone is buying into this trend. A 2018 study published in the Journal of Adolescent Health looked at the number of youth emergency room visits to the Denver Children’s Hospital Colorado for acute cannabis-related symptoms, finding an increase from 161 in 2005 to 777 in 2015, with spikes around the legalization of medical sales in 2009 and recreational legalization in 2014.
Self-reported surveys finding little change in teen cannabis use after legalization “may not reliably reflect the impact of legalization on adolescent health,” the authors concluded.
When the RAND Drug Policy Research Center published a researcher’s letter in JAMA Pediatrics reporting a decrease in cannabis use among Washington teens post-legalization, they included a plea for researchers to use representative surveys when trying to determine the relationship between legalization and youth cannabis use.
“These findings do not provide a final answer about how legalization ultimately may influence youth marijuana usage,” wrote study co-author and RAND co-director Rosalie Liccardo Pacula in the 2018 letter. “A variety of factors may influence the behavior of adolescents and those factors are likely to influence behaviors in different ways over time.”
One possibility that Anderson’s study points to is that “it is more difficult for teenagers to obtain marijuana as drug dealers are replaced by licensed dispensaries that require proof of age.”
This is the hope of lawmakers in legalized cannabis states — that restricted legal sales will replace an unregulated black market. But with illegal sales still accounting for as much as 80 percent of overall sales in states where recreational cannabis use has been made legal, some feel a different dynamic is in play.
One theory is that the risk of illegal cannabis is its own draw. Writing in Psychology Today on the phenomenon, Nathan H. Lents, Ph.D., invoked the evolutionary biology behavior of “costly signaling” to explain why stigmatization has been ineffective at deterring teen cannabis use.
“Most drug deterrence initiatives repeat the refrain that drugs are harmful and taboo,” Lent writes. “But this is precisely what makes them so attractive to teens, especially teenage boys. In their minds, it frames drug use as an opportunity to show off to others and advertise fitness.”