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Recreational cannabis legalization has passed in nearly half of the United States since 2012, and retail sales of the products have risen, but a new study by Boston College researchers finds no evidence that these two factors have contributed to a net increase in substance use among adolescents in the U.S.

The results, utilizing the most recent data on adolescent substance use to evaluate the effect of recreational cannabis legalization and retail sales on youth鈥檚 use of cannabis, tobacco, and alcohol, were .

The study鈥檚 authors鈥攃o-principal investigators Rebekah Levine Coley, a Lynch School of Education and Human Development professor; School of Social Work Professor Summer Sherburne Hawkins; and Economics Professor and Chair Christopher F. Baum鈥攁re among the first to evaluate associations between recreational cannabis legislation and recreational cannabis retail sales through 2021.

鈥淎lthough studies of early-enacting states and Canada reported few effects of recreational cannabis legislation on adolescent substance abuse, experts have highlighted the need to further assess policy outcomes in youth as legislation and retail availability spread, and other policies targeting youth substance use shift,鈥� the authors wrote. 鈥淲e found limited associations between recreational cannabis legalization and retail sales with adolescent substance use, extending previous findings.鈥�

The researchers analyzed data from nearly 900,000 high school students in 47 states over a 10-year period between 2011 and 2021.

Since 2012, 24 states and Washington, D.C., enacted recreational cannabis legislation, and 18 states implemented recreational cannabis sales.

According to the researchers, recreational cannabis legalization was associated with modest decreases in cannabis, alcohol, and e-cigarette use, while retail sales were associated with lower e-cigarette use, and a lower likelihood鈥攂ut also increased frequency鈥攐f cannabis use among youth consumers, leading to no overall change in cannabis use.

鈥淭he results suggest that legalization and greater control over cannabis markets have not facilitated adolescents鈥� entry into substance use,鈥� noted the co-authors.

According to the Pew Research Center, 54 percent of Americans live in a state where the recreational use of marijuana is legal, while 74 percent of Americans live in a state where marijuana is legal for either recreational or medical use.聽 Also, 79 percent of Americans live in a county with at least one cannabis dispensary; as of February 2024, there are nearly 15,000 dispensaries operating in the U.S.

Discussing the study recently, Coley said its results were not particularly surprising, given that they extended prior research by the team and others finding limited associations between recreational cannabis legislation and adolescent cannabis use. 聽

However, she added, 鈥済iven other evidence that recreational legalization has increased access to cannabis and been linked with increased use and problematic outcomes among adults, it is quite interesting that these patterns have not extended to adolescents. Teens are not legally allowed to purchase under the new laws, suggesting perhaps that legal sales are not increasing access to under-age adolescents in the same manner as increased access for adults.鈥�

Coley said parents, educators, and other adults would likely find comfort in the fact that evidence to date does not find increased adolescent use of cannabis鈥攐r of other substances due to spillover or substitution effects鈥攆ollowing recreational cannabis legalization.

鈥淕iven the potential risks of early entry into cannabis use, including mental health repercussions, other substance use as well as substance abuse, this is indeed good news,鈥� she said. 鈥淲e did identify one pattern of concern that is important to continue to track, however: the suggestion that, following enactment of recreational cannabis commercial sales, youths using cannabis were doing so more frequently.聽 As public views of the safety and accessibility of cannabis continue to evolve, along with potential legal repercussions of cannabis possession and use, it is important to continue to evaluate repercussions for adolescent substance use and well-being.鈥�

Researchers who contributed to the study included Naoka Carey, a doctoral candidate in the Applied Developmental and Educational Psychology Department of the Lynch School; and Claudia Kruzik, a postdoctoral research associate at the University of Maryland-College Park.