Trends in Marijuana Use

May 28, 2024 - Trajectory modeling of cannabis use over 30 years identifies five unique longitudinal patterns. This research publication (Mahar et al., 2023) is noteworthy in that it provides a picture of the long-term pattern of cannabis use across decades, something rare in the published literature.  The researchers used cannabis use data spanning about 30 years from the U.S. Coronary Artery Risk Development in Young Adults Cohort (CARDIA).   

By statistically creating trajectories of current cannabis use during young and middle adulthood, 5 unique patterns of cannabis use were identified.  The five groups spanning age 20 to approx. age 55 and their respective prevalence rates were the following: consistent high-level use (9%), declining high-level use (6%), declining moderate-level use (14%), consistent moderate-level use (11%), and consistent very low or non-use (59%). 

Note from this reviewer (KCW): The patterns of reported cannabis use trajectory spanning youth to middle-age adulthood are similar to what have been reported in the literature on the long-term course of alcohol use. 

May 24, 2024 - Changes in self-reported cannabis use in the United States from 1979 to 2022. Caulkins (2024) has published a study that capitalizes on national U.S. data across 27 surveys from 1979 to 2022 (total N = 1,641,041).  Whereas reported cannabis use declined to a nadir in 1992, with a partial recovery through 2008, substantial increases of cannabis use have occurred since then. This trend is particularly the case for intensive (daily or near daily; DND) use.

 By 2022, and for the first time since this national survey was conducted, there are more cannabis DND users (17.9 million) than alcohol DND users (14.7 million). This cannabis DND rate is still below the number of cigarette DND users (defined as smoked one or more packs of cigarettes per day).  But as Caulkins notes “patterns of marijuana consumption have shifted from being like alcohol to being closer to cigarette use.”

 The data reported by Caulkins show aggregated results across all age groups. There are no breakdowns of findings by the survey’s standard age groupings reported in its accessible data tables (12-17; 18-25; 26+). Yet the author notes “It (cannabis) is also no longer a young person’s drug. In 2022, people 35 and older accounted for (slightly) more days of use than did those under the age of 35.”

May 15, 2024 - The Impact of Recreational Cannabis Markets on Cannabis Use Among Adolescents and Adults: A Synthetic Control Analysis. This study (Marinello, 2024) capitalized on state-level data from the National Survey on Drug Use and Health (NSDUH) to examine the effect of legal recreational markets on prevalence and initiation of cannabis use in Colorado, Washington, Oregon, Alaska, and Nevada.  Given NSDUH’s age grouping in the accessible database, the author reported results separately for adolescents (12-17), young adults (18-25), and older adults (26 and older).

Why these five states? Each had been a legal recreational cannabis state for several years, which permitted the author to look at effects early after legalization (1 year) and later (2-4 years).  As many epidemiologists have noted, reliable effects of legalization are best viewed when a reasonable time interval has passed after retail sales are available. 

The analysis showed that legalization was associated with moderate to large increases in initiation and prevalence of use among all age groups, with increases larger in the second post-legalization period and among young adults (18-25). The author speculates these reasons for the larger effect during this second period: more markets available, lower costs, greater accessibility, normalization of use with consequential reductions in risk perceptions, increased popularity, development of new products, and expanded marketing.

October 4, 2023 - Cannabis Use Frequency and Cannabis-Related Consequences in High-Risk Young Adults Across Cannabis Legalization. This study from Canada published by Doggett and colleagues (2023) examined changes in cannabis use frequency and cannabis-related consequences pre- and post-recreational cannabis legalization in Canada in a longitudinal sample of young adults (N=619) with a history of “2 or more heavy episodic drinking episodes.” 

The main overall finding was that there was an average decrease in cannabis use frequency and consequences across legalization. But a major caveat was that pre-legalization cannabis use pattern moderated this finding, a point absent from many media coverages of this study.  The young adults that were frequent cannabis users pre-legalization exhibited reductions, a pattern consistent with the well-documented developmental pattern that young adults “age out” of substance use during this age period.  Yet those not using cannabis pre-legalization showed the opposite trend; this group reported increases in cannabis use over time.   

The study authors caution that the sample is a select group and the findings do not provide a rigorous assessment of the possible effects of cannabis legalization on changes of use frequency and resulting consequences.

August 27, 2022 - Impacts of Recreational Cannabis Legalization on Cannabis Use: A Longitudinal Discordant Twin Study. This study used a twin study method to examine the issue of the effect of recreational legalization on adult (age 24-47-years-old) cannabis use frequency and sources of variance across legal environments. The twins (total N = ~3400) were assessed longitudinally, which allowed a pre- and post-legalization trend analysis. Cannabis use frequency among identical (monozygotic) twins discordant for living in legal/illegal states were also examined.  

Accounting for pre-2014 use, residents of legal states used cannabis more frequently than residents of illegal states, and this finding was confirmed with discordant identical twins. Overall, there was a  20% average increase in cannabis use frequency attributable to recreational legalization. 

There was a genetic effect: The genetic correlation between cannabis use before and after legalization was higher in states that had not legalized.

August 14, 2022 - Estimating the Effects of Legalizing Recreational Cannabis on Newly Incident Cannabis Use. This is another of a recent set of articles that examines the question of the impact of state’s legalizing commercial sales of cannabis on changes in cannabis use.  The authors of this study used US survey data between 2008 and 2019 to focus on “estimated occurrence of newly incident cannabis use” associated with state-level  commercial legalization of cannabis.  Study results indicated (1) no policy-associated

changes in the occurrence of newly incident cannabis onsets for underage persons (i.e., < 21 years of age) but an increased occurrence of newly onset cannabis use among older adults (i.e., >21 years). 

Commentary from this writer (KCW): 

1. An important context of this study: The authors focused on just one dimension of cannabis use: newly onset use of cannabis.  Numerous other studies of state-level commercial legalization of cannabis have reliably shown increases in underage youth with respect to (1) frequency of use among current users, and (2) prevalence rate of Cannabis Use Disorder. 

2. It would have been preferred if the authors had limited the state-level data to those states that have enacted commercial sales of cannabis for several years and not have included states where enactment was very recent. Why? An epidemiological principle is that the impact on behavior of a change in public health policy often takes a few years for it to manifest.

July 20, 2021 - Joint perceptions of the risk and availability of Cannabis. In this study using national data from the National Surveys on Drug Use and Health from 2002-2018, which involved survey results from nearly one million individuals age 12 and older, the researchers analyzed the inter-relationship of cannabis use, perception of cannabis use risk, and perception of cannabis availability.  The findings were somewhat expected.  Respondents who perceived cannabis as low-risk were six times more likely to have used cannabis in the past-year than individuals who perceived the drug as high-risk. Also, individuals who perceived cannabis as available were five times more likely to have used cannabis in the past year than individuals who perceived it as unavailable. Among individuals who perceived cannabis as both low-risk and available, they were 22 times more likely to have used the drug in the past year than those who perceived cannabis as both high-risk and unavailable.

January 16, 2019: Your brain on drugs. But before we take the next logical step toward legalized marijuana for all, maybe we should ask for more research about how it affects our brains. And the brains of our kids.

January 14, 2019: A note of caution as state weighs legalizing pot. Chronic users are likely to bear the brunt of the costs, and be most vulnerable to potential problems.

December 19, 2018: Cannabis for Christmas? In Minnesota, CBD products are hot this holiday

December 19, 2018: Past-month marijuana use up one-third among eighth-graders, doubles among tenth-graders, nearly doubles among twelfth-graders since 1992. A legalization movement that began in the early 1990s saw its first success in 1996 when California legalized marijuana for medical use, and legalization for both medical and recreational use took off as more states copied California’s lead. One result? An escalation of marijuana use among the nation’s adolescents.

December 3, 2018: Annual HHS Survey Finds Marijuana Use Higher in “Legal” States: Colorado leads nation for first time in adolescent pot use. Legal states use rates nearly 45% higher than other states. Alcohol use also up in Colorado.