An updated study was published in The Journal of Medical Research on May 9, 2009. Journal of Adolescent HealthThe evidence shows that marijuana legalization has led to a decrease in the youth’s use of tobacco and alcohol. Entitled “Trends in Alcohol, Cigarette, E-Cigarette, and Nonprescribed Pain Reliever Use Among Young Adults in Washington State After Legalization of Nonmedical Cannabis,” the study includes the analysis of six waves of survey data collected between 2014 and 2019. The University of Washington researchers reviewed the data of approximately 12,500 teenagers.

“Prevalence of past-month alcohol use, heavy episodic drinking (HED), and cigarette use and prevalence of past-year pain reliever misuse decreased, while the prevalence of past-month e-cigarette use increased since 2016 (the first year assessed),” researchers wrote about the results. “Across years and age groups, the prevalence of substance use other than cannabis was higher among occasional and frequent cannabis users compared to cannabis nonusers.”

These habits changed over time as legalization became more common in states. “However, associations between both occasional (1–19 days in the prior month) and frequent (20+ days) cannabis use and pain reliever misuse and between frequent cannabis use and HED weakened over time among individuals ages 21–25.”

“Contrary to concerns about spillover effects, implementation of legalized nonmedical cannabis coincided with decreases in alcohol and cigarette use and pain reliever misuse,” researchers concluded.

It is recommended that further research be done to understand the impact of legalization on youth use. “The weakening association of cannabis use with the use of other substances among individuals ages 21–25 requires further research but may suggest increased importance of cannabis-specific prevention and treatment efforts,” researchers wrote.

Numerous other studies have examined the impact of marijuana on young adults. The negative portrayal of cannabis on TikTok by youths who use it frequently was questioned in a study that was published this week.

In March 2022, a policy paper released by the Coalition for Cannabis Policy, Education and Regulation (CPEAR) analyzed youth cannabis consumption as well, and also reported that youth cannabis consumption hasn’t increased since legalization began. It was concluded that the federal structure to prevent youth from using cannabis is vital and should be maintained.

A second study, analyzing 46 states, and using data from 1991 to 2015, was published in March 2021. “This study found no evidence between 1991 and 2015 of increases in adolescents reporting past 30-day marijuana use or heavy marijuana use associated with state MML (medical marijuana law) enactment or operational MML dispensaries,” the authors wrote in their abstract.

In 2020, another study looked at the impact of legalization on California youth. It found little effect in California. “Contrary to the claims of many legalization opponents, changes in states’ marijuana policies have not led to any significant rise in cannabis use among young people,” NORML Deputy Director Paul Armentano said about the study. “Overall, most voters believe that these adult-use policies are operating as intended, which is why no state that has legalized the use of cannabis for either medical or adult-use purposes has ever repealed their law.”

These studies go back to the earlier years of adult-use legalization, as seen in published findings from 2016 from the Colorado Health Department who found teens saying that four out of five high school students “say they don’t use marijuana, even occasionally.”

While these studies help show that youth cannabis consumption has not increased, there is still the question of how cannabis consumption affects young adults’ minds. According to 2016 research, some studies suggest that smoking causes grades declines more than marijuana. However, in 2018 a study found evidence that kid’s cognitive development can be affected, followed by another study in 2019 that found no link between adolescent cannabis consumption and adult brain structure. There is conflicting evidence, so more research is needed in order to find out more about cannabis’ effects on adolescents.