Age-Varying Patterns of Cannabis Use, Related Risk Factors, and their Associations among Young Adults in the Context of Legalized Nonmedical Cannabis.

The current study examined age-varying patterns of cannabis use, cannabis-specific risk factors, and their associations across young adulthood. We used repeated cross-sectional data from young adults (N = 15,251; Mage = 22.02 years, SDage = 2.22; 68% female) who enrolled in the annual, statewide Washington Young Adult Health Survey between 2015 and 2022. Logistic time-varying effect models showed that cannabis use increased from ages 18-22 and remained relatively stable through age 26. Most cannabis-specific risk factors increased gradually across young adulthood, although perceptions of cannabis use acceptability (injunctive norms) increased substantially through age 23 followed by decreases. Ease of obtaining cannabis, perceptions about others' use (descriptive norms), and low perceived physical harm were generally associated with any past-month cannabis use with stronger associations around age 18. Injunctive norms and low perceived psychological harm were consistently associated with past-month use across young adulthood. Ease of obtaining cannabis, injunctive norms, descriptive norms, and low psychological harm were associated with frequent cannabis use across young adulthood with associations strongest prior to age 21. Low perceived physical harm was associated with frequent use across young adulthood with associations getting somewhat stronger across ages. Findings underscore the importance of focusing on cannabis-specific risk factors in preventive intervention efforts over the course of young adulthood, including focus on young adults in their mid- 20 s in the context of legalized cannabis.