Opponents of marijuana legalization frequently warn that it will lead to rampant cannabis consumption by teenagers. But two studies published in November found that legalization has not been associated with increases in adolescent marijuana use or addiction. In fact, there is some evidence that both decline when pot prohibition is repealed for adults.
Boston College psychologist Rebekah Levine Coley and four other researchers looked at trends in marijuana use among teenagers in 47 states, as measured by the Youth Risk Behavior Survey, from 1999 to 2017. During that period, eight states and the District of Columbia legalized recreational marijuana use by adults 21 or older.
"We found no evidence that [recreational legalization] was associated with increased likelihood or level of marijuana use among adolescents," Coley and her colleagues reported in the Journal of Adolescent Health. "Rather, among adolescents who reported any use of marijuana in the past month, the frequency of use declined by 16%."
That finding suggests shifting the supply of marijuana from black-market dealers to state-licensed retailers who enforce a minimum purchase age helps curtail adolescent access, even if legalization also increases purchases by adult relatives and acquaintances. Legalization may also reduce marijuana's "forbidden fruit" appeal to teenagers.
Coley et al.'s finding that legalization is associated with less-frequent use among adolescent cannabis consumers is consistent with the results of a study that looked at trends in addiction treatment admissions. Between 2008 and 2017, Temple University health geographer Jeremy Mennis found, the number of "adolescent treatment admissions for marijuana" per 10,000 teenagers fell by nearly half nationwide, and the downward trend was especially sharp in states that legalized recreational use for adults.
Seven of those eight states "fall into the class with the steepest level of admissions decline," Mennis reported in a study published by the Centers for Disease Control and Prevention. "This research suggests that a precipitous national decline in adolescent treatment admissions, particularly in states legalizing recreational marijuana use, is occurring simultaneously with a period of increasing permissiveness, decreasing perception of harm, and increasing adult use, regarding marijuana."
Since most teenagers admitted to treatment for marijuana use end up there after getting into legal trouble, this decline may be partly due to changes in law enforcement practices. But a 2019 study in the journal Drug and Alcohol Dependence suggests the admissions trend also reflects real changes in adolescent behavior. Between 2002 and 2016, according to survey data, the prevalence of "cannabis use disorder" fell by 27 percent among teenagers who used marijuana frequently.