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Estimating the effects of legalizing recreational cannabis on newly incident cannabis use.

ABSTRACT: Liberalized state-level recreational cannabis policies in the United States (US) fostered important policy evaluations with a focus on epidemiological parameters such as proportions [e.g., active cannabis use prevalence; cannabis use disorder (CUD) prevalence]. This cannabis policy evaluation project adds novel evidence on a neglected parameter-namely, estimated occurrence of newly incident cannabis use for underage (<21 years) versus older adults. The project's study populations were specified to yield nationally representative estimates for all 51 major US jurisdictions, with probability sample totals of 819,543 non-institutionalized US civilian residents between 2008 and 2019. Standardized items to measure cannabis onsets are from audio computer-assisted self-interviews. Policy effect estimates are from event study difference-in-difference (DiD) models that allow for causal inference when policy implementation is staggered. The evidence indicates no policy-associated changes in the occurrence of newly incident cannabis onsets for underage persons, but an increased occurrence of newly onset cannabis use among older adults (i.e., >21 years). We offer a tentative conclusion of public health importance: Legalized cannabis retail sales might be followed by the increased occurrence of cannabis onsets for older adults, but not for underage persons who cannot buy cannabis products in a retail outlet. Cannabis policy research does not yet qualify as a mature science. We argue that modeling newly incident cannabis use might be more informative than the modeling of prevalences when evaluating policy effects and provide evidence of the advantages of the event study model over regression methods that seek to adjust for confounding factors.

SUBMITTER: Montgomery BW

PROVIDER: S-EPMC9302774 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundCannabis use and cannabis regulatory policies recently re-surfaced as noteworthy global research and social media topics, including claims that Mexicans have been sending cannabis and other drug supplies through a porous border into the United States. These circumstances prompted us to conduct an epidemiological test of whether the states bordering Mexico had exceptionally large cannabis incidence rates for 2002-2011. The resulting range of cannabis incidence rates disclosed here can serve as 2002-2011 benchmark values against which estimates from later years can be compared.MethodsThe population under study is 12-to-24-year-old non-institutionalized civilian community residents of the US, sampled and assessed with confidential audio computer-assisted self-interviews (ACASI) during National Surveys on Drug Use and Health, 2002-2011 (aggregate n ∼ 420,000) for which public use datasets were available. We estimated state-specific cannabis incidence rates based on independent replication sample surveys across these years, and derived meta-analysis estimates for 10 pre-specified regions, including the Mexico border region.ResultsFrom meta-analysis, the estimated annual incidence rate for cannabis use in the Mexico Border Region is 5% (95% CI [4%-7%]), which is not an exceptional value relative to the overall US estimate of 6% (95% CI [5%-6%]). Geographically quite distant from Mexico and from states of the western US with liberalized cannabis policies, the North Atlantic Region population has the numerically largest incidence estimate at 7% (95% CI [6%-8%]), while the Gulf of Mexico Border Region population has the lowest incidence rate at 5% (95% CI [4%-6%]). Within the set of state-specific estimates, Vermont's and Utah's populations have the largest and smallest incidence rates, respectively (VT: 9%; 95% CI [8%-10%]; UT: 3%; 95% CI [3%-4%]).DiscussionBased on this study's estimates, among 12-to-24-year-old US community residents, an estimated 6% start to use cannabis each year (roughly one in 16). Relatively minor variation in region-wise and state-level estimates is seen, although Vermont and Utah might be exceptional. As of 2011, proximity to Mexico, to Canada, and to the western states with liberalized policies apparently has induced little variation in cannabis incidence rates. Our primary intent was to create a set of benchmark estimates for state-specific and region-specific population incidence rates for cannabis use, using meta-analysis based on independent US survey replications. Public health officials and policy analysts now can use these benchmark estimates from 2002-2011 for planning, and in comparisons with newer estimates.

Project description:AimsTo estimate the effect of recreational legalization on cannabis use frequency and sources of variance across legal environments.DesignLongitudinal discordant twin and gene-environment interaction models in twins recruited from birth records and assessed prospectively.SettingThe United States, including states with different recreational cannabis policies before and after 2014, when recreational cannabis was first legalized.ParticipantsTwo longitudinal, prospectively assessed samples of American twins aged 24-47 (n = 1425 in legal states, n = 1996 in illegal states), including 111 monozygotic pairs discordant for residence.MeasurementsCurrent cannabis use frequency (measured continuously and ordinally) was the primary outcome, and the predictor was recreational status of cannabis (legal/illegal) in the participant's state of residence at the time of assessment. Covariates include age, sex and cannabis use frequency prior to 2014.FindingsAccounting for pre-2014 use, residents of legal states used cannabis more frequently than residents of illegal states (b = 0.21, P = 8.08 × 10-5 ). Comparing 111 pairs of monozygotic twins discordant for residence confirmed the effect (b = 0.18, P = 0.014). There was inconclusive evidence for genetic influences on cannabis use frequency that were specific to the legal environment [χ2 = 2.9 × 10-9 , degrees of freedom (d.f.) = 1, P > 0.999]. Existing genetic influences were moderated by the legal environment, as the genetic correlation between marijuana use before and after legalization was lower in states that legalized (rgenetic = 0.24) compared with states that did not (rgenetic = 0.78, Pdifference = 0.016).ConclusionsIn the United States, there appears to be a ~ 20% average increase in cannabis use frequency attributable to recreational legalization, consistent across increasingly rigorous designs. In addition, the heritability of cannabis use frequency appears to be moderated by legalization.

Project description:ImportanceMedical and nonmedical cannabis use and cannabis use disorders (CUD) have increased with increasing cannabis legalization. However, the prevalence of CUD among primary care patients who use cannabis for medical or nonmedical reasons is unknown for patients in states with legal recreational use.ObjectiveTo estimate the prevalence and severity of CUD among patients who report medical use only, nonmedical use only, and both reasons for cannabis use in a state with legal recreational use.Design, setting, and participantsThis cross-sectional survey study took place at an integrated health system in Washington State. Among 108 950 adult patients who completed routine cannabis screening from March 2019 to September 2019, 5000 were selected for a confidential cannabis survey using stratified random sampling for frequency of past-year cannabis use and race and ethnicity. Among 1688 respondents, 1463 reporting past 30-day cannabis use were included in the study.ExposurePatient survey-reported reason for cannabis use in the past 30 days: medical use only, nonmedical use only, and both reasons.Main outcomes and measuresPatient responses to the Composite International Diagnostic Interview-Substance Abuse Module for CUD, corresponding to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition CUD severity (0-11 symptoms) were categorized as any CUD (≥2 symptoms) and moderate to severe CUD (≥4 symptoms). Adjusted analyses were weighted for survey stratification and nonresponse for primary care population estimates and compared prevalence of CUD across reasons for cannabis use.ResultsOf 1463 included primary care patients (weighted mean [SD] age, 47.4 [16.8] years; 748 [weighted proportion, 61.9%] female) who used cannabis, 42.4% (95% CI, 31.2%-54.3%) reported medical use only, 25.1% (95% CI, 17.8%-34.2%) nonmedical use only, and 32.5% (95% CI, 25.3%-40.8%) both reasons for use. The prevalence of CUD was 21.3% (95% CI, 15.4%-28.6%) and did not vary across groups. The prevalence of moderate to severe CUD was 6.5% (95% CI, 5.0%-8.6%) and differed across groups: 1.3% (95% CI, 0.0%-2.8%) for medical use, 7.2% (95% CI, 3.9%-10.4%) for nonmedical use, and 7.5% (95% CI, 5.7%-9.4%) for both reasons for use (P = .01).Conclusions and relevanceIn this cross-sectional study of primary care patients in a state with legal recreational cannabis use, CUD was common among patients who used cannabis. Moderate to severe CUD was more prevalent among patients who reported any nonmedical use. These results underscore the importance of assessing patient cannabis use and CUD symptoms in medical settings.

Project description:BackgroundThere has been a precipitous decline in authorizations for medical cannabis since non-medical cannabis was legalized in Canada in 2018. This study examines the demographic and health- and medical cannabis-related factors associated with authorization as well as the differences in medical cannabis use, side effects, and sources of medical cannabis and information by authorization status.MethodsIndividuals who were taking cannabis for therapeutic purposes completed an online survey in early 2022. Multivariable logistic regression was used to determine odds ratios (OR) and 95% confidence intervals (CI) of demographic and health- and medical cannabis-related variables associated with holding medical cannabis authorization. The differences in medical cannabis use, side effects, and sources of information by authorization status were determined via t-tests and chi-squared analysis.ResultsA total of 5433 individuals who were currently taking cannabis for therapeutic purposes completed the study, of which 2941 (54.1%) currently held medical authorization. Individuals with authorization were more likely to be older (OR ≥ 70 years vs. < 30 years, 4.85 (95% CI, 3.49-6.76)), identify as a man (OR man vs. woman, 1.53 (1.34-1.74)), have a higher income (OR > $100,000/year vs. < $50,000 year, 1.55 (1.30-1.84)), and less likely to live in a small town (OR small town/rural vs. large city, 0.69 (0.59-0.81)). They were significantly more likely to report not experiencing any side effects (29.9% vs. 23.4%; p < 0.001), knowing the amount of cannabis they were taking (32.1% vs. 17.7%; p < 0.001), obtaining cannabis from regulated sources (74.1% vs. 47.5%; p < 0.001), and seeking information about medical cannabis from healthcare professionals (67.8% vs. 48.2%; p < 0.01) than individuals without authorization.ConclusionsThese findings offer insight into the possible issues regarding equitable access to medical cannabis and how authorization may support and influence individuals in a jurisdiction where recreational cannabis is legalized, highlighting the value of a formal medical cannabis authorization process.

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Estimating the effects of legalizing recreational cannabis on newly incident cannabis use.

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