Frequent cannabis use rose among California teens after legalization

A study in California found that cannabis use became more frequent among 11^th graders in California after recreational cannabis retail was legalized. Eleventh graders in cities with no cannabis shops at all, neither recreational nor medical ones, tended to use cannabis less often compared to their peers in places where cannabis stores were allowed. The paper was published in the Journal of Adolescent Health.

Cannabis is a plant genus whose flowers and leaves contain psychoactive compounds called cannabinoids, the most notable being THC and CBD. It has been used for thousands of years for medicinal, recreational, and industrial purposes. When consumed, cannabis can alter perception, mood, and cognition by interacting with the brain’s endocannabinoid system. Although widely used, cannabis remains regulated or illegal in many parts of the world due to concerns about health, safety, and dependence.

In California, personal possession and cultivation of cannabis were legalized in 2016. In 2018, recreational cannabis retail was legalized as well. However, local jurisdictions retained the right to prohibit cannabis retail sales in their areas. By January 2024, 59% of Californian jurisdictions allowed legal cannabis retail sales (while 41% did not).

Shops legally selling cannabis are called cannabis dispensaries. Cannabis dispensaries sell various cannabis products—such as dried flower, edibles, oils, and concentrates—for non-medical, adult use legally in jurisdictions that permit this. These stores operate under strict government regulations that control licensing, age limits, product testing, packaging, and taxation. Usually, retailers must follow rules about advertising, security, and responsible sales practices. One of the greatest concerns of legalizing recreational cannabis retail is the potential impact on youth use and subsequent harms. In adolescence, the brain develops quickly and is very susceptible to adverse health effects, including those that could be associated with cannabis use.

Study author Bethany J. Simard and her colleagues wanted to explore the changes in cannabis use among California 11^th graders before and after the statewide legalization of recreational cannabis retail. They also wanted to see whether these changes differ according to the cannabis policy applied by the local jurisdiction.

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The study authors analyzed data from the California Healthy Kids Survey collected in multiple waves between 2015 and 2020. It is an annual survey of 7^th, 9^th, and 11^th grade students conducted by the California Department of Education. Among other things, the survey asked participating students about cannabis use.

More specifically, it asked how many days in the past 30 days they used “marijuana (pot, weed, grass, hash, or bud)” in 2015/16—2016/17 and “marijuana (smoke, vape, eat, or drink)” for years 2017/18—2019/20. Study authors also took into account cannabis retail policies in the jurisdiction where each participating student’s school was located.

Results showed that the odds that a student would report any use of cannabis in the past 30 days increased by 6% immediately after legalization. This happened in all jurisdictions except in those allowing medical delivery only; in those jurisdictions, the odds that students would report use in the past 30 days slightly decreased. However, regarding frequent use (20 or more days a month), the increase was much sharper: by spring 2020, the odds of frequent use were 30% higher.

The odds of recent cannabis use and frequent cannabis use were lower in jurisdictions that banned both recreational cannabis retail and that did not allow medical cannabis stores before legalization compared to jurisdictions that allowed storefronts. In other words, 11^th graders in cities with no cannabis shops at all, neither recreational nor earlier medical ones, tended to use cannabis less often compared to their peers in places where cannabis stores were allowed.

“Frequent cannabis use among California 11th graders increased post-RCR legalization [after recreational cannabis retail legalization]. After an increase in any 30-day use, use in retail-banning jurisdictions declined, whereas rates in jurisdictions newly permitting storefronts and delivery remained raised,” study authors concluded.

The study sheds light on the changes in cannabis use associated with the legalization of recreational cannabis retail. However, it should be noted that the study took into account cannabis policies in locations of schools, not in places where students’ homes are located. It also did not take into account cannabis policies in neighboring jurisdictions.

The paper, “Local Cannabis Policy and Cannabis Use by California High School Students Before and After Statewide Retail Legalization,” was authored by Bethany J. Simard, Alisa A. Padon, Lynn D. Silver, David S. Timberlake, and Kelly C. Young-Wolff.