New Research from the Journal of Adolescent Health reveals critical insights about how cannabis legalization affects youth behavior, and why local policies matter more than ever. The study, led by researchers at the Public Health Institute, Kaiser Permanente and University of California, examined cannabis use among over 377,000 California high school juniors before and after the state legalized recreational cannabis retail in 2018.

The findings highlight an alarming trend: Frequent cannabis use among teens increased significantly after legalization, particularly in communities that permitted retail storefronts and delivery.

What the Research Shows:

  • Teen cannabis use increased significantly following legalization (except in areas that permitted only medical delivery of cannabis products).
  • Frequent use, defined as 20 or more days a month, grew the most, reversing a previous downwards trend and continued to increase through 2020.
  • Communities that banned retail cannabis sales entirely, consistently had lower rates of youth use, both before and after legalization.
  • Local policies made an impact. Jurisdictions that allowed storefront or delivery sales saw a significantly higher rate of use among high school juniors.

 Why Does This Matter for Prevention?

  • Teen Vulnerability– The teenage brain is still developing until the mid-twenties, making it especially sensitive to substances like THC. Early cannabis use has been linked to problems with memory, mental health disorders and increased risk of addiction.
  • Frequent use– Using marijuana on 20 or more days per month is a serious concern for teens. Regular or heavy use greatly increases the risk of dependency and the development of cannabis use disorder, potentially disrupting academic, social, and emotional growth.
  • Increased exposure– Legalization brings broader marketing, normalized use and greater access, especially when retail stores and delivery services are allowed in local neighborhoods/communities.

Recommendations for Communities:

  • Adapt or maintain retail bans to limit access and reduce normalization of use.
  • Restrict cannabis marketing, particularly near schools or on digital platforms frequently visited by young people.
  • Support local prevention coalitions to help educate families and youth about the real risks of early cannabis use.
  • Have open conversations with teens.

 The Bottom Line:

Legalization does not mean safety. As this study demonstrates, when cannabis becomes more visible and accessible, youth use follows. Communities that stand firm with restrictive policies and invest in prevention can make a real difference in protecting their teens.

Read the full article here: https://www.jahonline.org/article/S1054-139X(25)00417-3/fulltext

You can also access a wide range of science-based educational materials at One Page Resources – Drug Free America Foundation

References:

Simard, Bethany J., et al. “Local cannabis policy and cannabis use by California High School students before and after statewide retail legalization.” Journal of Adolescent Health, Oct. 2025, https://doi.org/10.1016/j.jadohealth.2025.09.003.