Adolescent Cannabis Use and Perceived Social Norm Trends Pre- and Post-Implementation of Washington State's Liberalized Recreational Cannabis Policy: Healthy Youth Survey, 2008-2018.

This study examined trends in adolescent perceptions of social norms pertaining to adolescent cannabis use, in relation to past 30-day adolescent cannabis use, and was interpreted in light of Washington State's liberalized recreational cannabis policy (LRCP: 2012). Data come from Washington's Healthy Youth Survey (HYS), collected during even-numbered years between 2008 and 2018, with methods-stabilized surveys of school-attending youths in grades 8, 10, and 12. This study used an aggregate state census sample of n = 325,723. Year-specific social norms and cannabis use proportions were estimated, stratified by grade. Regression analyses assessed associations between social norms and recent cannabis use. The proportion of recent adolescent cannabis use during the initial years post-LRCP in Washington State remained relatively stable or trended downward slightly; however, 2018 data may indicate a slight upward trend for 10th and 8th graders. Cannabis use by a close friend consistently paralleled adolescent cannabis use trends. The proportion of youth reporting parental acceptance of, and overall community acceptance of, adolescent cannabis use trended slightly upward in 2014 (post-LRCP implementation) but, since, has remained stable or declined slightly. Adolescent self-acceptance of youth cannabis use increased steadily for high school students between 2008 and 2014, edged downward in 2016, and then trended back upward for 8th and 10th graders in 2018. Perceived parental acceptance remained statistically associated with adolescent cannabis use across grades and years, with the strength of associations edging up. Ongoing monitoring of substance use and related risk factor trends will be needed to understand the impacts of LRCPs.