Purpose: Cannabis use during adolescence can have harmful consequences, including poor educational outcomes, neurocognitive defects, and an increased risk of addiction to other drugs, such as tobacco, alcohol, and opioids. Perceived family and social network cannabis use is a risk factor for use among adolescents. It is not currently known whether there is an association between perceived family/social network cannabis use and adolescent cannabis use in the context of legalization. The purpose of this study was to examine associations between adolescent perceptions of parent, sibling, and best friend medical and/or recreational cannabis use and adolescents' own use and whether the association changed pre-legalization and post-legalization in Massachusetts.

Methods: We analyzed responses from surveys administered to students at 2 high schools in Massachusetts before legalization in 2016 (wave 1) and after legalization but before the start of regulated retail cannabis sales in 2018 (wave 2). We used χ2 tests and multiple logistic regression to examine associations between adolescent perception of parent, sibling, and best friend use and adolescent past 30-day cannabis use before and after legalization.

Findings: In this sample, no statistically significant differences were found in the prevalence of past 30-day cannabis use before and after legalization among adolescents. There was an increase in the proportion of adolescents who reported any perceived parent cannabis use from before to after legalization (18% before legalization to 24% after legalization; P = 0.018). Perceived parent, sibling, and best friend medical and recreational cannabis use were all associated with an increased odds of adolescent use, with the highest increase in odds found for perceived best friend use (adjusted odds ratio, 17.2; 95% CI, 12.4-24.0).

Implications: Adolescent perceptions of their parents as cannabis users increased after legalization, even before state-regulated retails sales began. Parent, sibling, and best friend cannabis use is each independently associated with increased odds of adolescent's own use. These findings from 1 Massachusetts district should be explored in larger and more representative populations and motivate additional attention to interventions that consider family and friend influences when seeking to address adolescent cannabis use.