The prevalence of cannabis use and cannabis–tobacco co-use has increased among young adults. Blunt use is a particularly salient form of co-use, as individuals who use blunts tend to initiate cannabis at younger ages, use more frequently, and are more likely to engage in other substance use. Although evidence is mixed as to whether tobacco and cannabis function as substitutes or complements, cannabis legalization may alter patterns of both substances, especially co-use among young adults. Existing studies on cannabis legalization and tobacco use have focused largely on adolescent cigarette smoking, and research on blunt use remains limited. The present study uses Joinpoint trend analysis—which identifies statistically significant changes in prevalence over time and their alignment with policy timing, rather than relying solely on pre–post comparisons—to examine 16-year trends in cannabis, blunt, cigarette, and cigar use among young adults in the context of changing cannabis policies.
The study analyzed 2-year state-level NSDUH data from 2002 to 2019 for young adults aged 18–25 residing in states that had implemented either adult-use plus medical-use (AMU) or medical-use-only (MUO) cannabis policies. Primary outcomes were past 30-day use of cannabis (across various modes of administration), blunts (cigars containing marijuana), and tobacco (cigarettes and cigars made only of tobacco, including cigarillos, large cigars, and small cigars resembling cigarettes). Information on the dates of cannabis policy adoption, effective dates, and retail sales initiation was obtained from the Marijuana Policy Project and the National Conference of State Legislatures. Using Joinpoint segmented regression models, we estimated temporal trends in product use and identified points of inflection (Joinpoints) for each state and by policy type (AMU vs. MUO), tested differences in trends between the two policy groups, and conducted a sensitivity analysis restricted to post-implementation data.
Most states showed increases in cannabis and blunt use among young adults over the 16-year period, with AMU states experiencing larger increases than MUO states. Cigarette and cigar use declined over time in both AMU and MUO states, with broadly similar trends by policy type. In 2018/2019, AMU states had lower cigarette smoking (16% vs. 19%) but higher cannabis use (29% vs. 21%) than MUO states; by this time, all AMU states—and three MUO states with post-effective data—had higher prevalence of cannabis use than cigarette smoking. In all AMU states, blunt use eventually surpassed cigar smoking, whereas in most MUO states, blunt and cigar use remained at similar levels. Joinpoint analyses showed that many trend changes in cannabis and blunt use did not clearly align with cannabis policy events, though in some AMU and MUO states (e.g., Maine, Nevada, Colorado, Delaware) increases or shifts in cannabis and/or blunt use appeared to follow the implementation of medical use laws or the opening of retail outlets. For cigarettes and cigars, all states showed at least one Joinpoint, with many declines beginning around 2009–2012 or 2014/2015; in several states, these declines coincided in timing with implementation of medical or adult-use cannabis laws and the opening of cannabis retail outlets, although some states (e.g., Delaware and Ohio) showed increases in cigar use over the same period.
Takeaway: Cannabis and blunt use increased more in AMU than in MUO states, but these differences are observational and may reflect broader state-level policy and social contexts rather than causal effects of cannabis laws alone.