San Francisco, CA – WestEd announces the release of the first comprehensive study of marijuana use among California adolescents since the November 2016 legalization of adult use. The study uncovers how frequency of use is changing and how usage is related to educational, behavioral, and social-emotional challenges.

This two-volume study (volume 1 and volume 2) completed by WestEd and funded by the California Department of Health Care Services, summarizes statewide data provided by students in grades 7, 9, and 11 who participated in the 2017/19 Seventeenth Biennial State California Healthy Kids Survey. One major finding of the study is that current use of marijuana is now as common as alcohol use, with almost 10 percent of 11th graders reporting frequent use of marijuana. This finding indicates the previous decline in marijuana use that began during 2011/13 may be ending. Relatedly, almost half of 11th graders reported that marijuana was easily available and easier to obtain than alcohol.

The study documents challenges associated with current use, particularly frequent use, among 11th graders. Among the most concerning findings is the significantly higher level of poor mental health among students who report marijuana usage. Current users are more likely to experience educational, behavioral, and social-emotional problems that increased with frequency of use, including lower school connectedness, attendance, and academic performance, and higher levels of victimization and violence perpetration at school.

Trends in perceived harmfulness, disapproval, and availability of marijuana are consistent with the broader trend of increasing adolescent marijuana use. Results show that student perceptions of the harmfulness of occasional marijuana use and their disapproval of marijuana experimentation are markedly declining, while previous declines in perceived availability of marijuana leveled off and even increased slightly among 9th graders.

The report also provides new information about the popularity of marijuana edibles and use of vaping devices, which may contribute to the increase in usage. For example, half of those students who report marijuana usage have reportedly engaged in all three methods of ingestion (smoking, vaping, and oral).

The two-volume report and the full results from the 2017/19 Biennial State California Healthy Kids Survey can be downloaded at

About the California Healthy Kids Survey

The California Healthy Kids Survey (CHKS) is a comprehensive whole child, school climate, and youth risk behavior data collection service available to all California local education agencies, and is funded by the California Department of Education. It is designed to efficiently and cost-effectively provide school districts and their partner communities with data that can be used to improve student academic performance and the social-emotional and behavioral health of all youth. The service is also available to states outside of California. The Biennial State CHKS, funded by the California Department of Health Care Services, collects CHKS data from a randomly selected sample of secondary schools, providing results that are representative of all students in grades 7, 9, and 11 in California.