A large US study found that when individual states legalised recreational cannabis, usage spread significantly, especially among younger people, according to a study in Addiction.
The study, of more than 20,000 Americans, compared four US states with legalised recreational cannabis (California, Massachusetts, Nevada and Maine) with states that had not, and is the first to estimate the link between recreational cannabis laws and individual-level changes in cannabis use among a nationally representative longitudinal cohort. It examines cannabis use initiation in both youths and adults.
It has a much larger sample size than similar longitudinal studies: 6,925 youths and 14,938 adults, 21,863 in total. The study provides evidence against the claim that legalisation would not increase cannabis use among youth.
According to a 2020 Natural Survey on Drug Use and Health, 17.9% of people aged 12 or older (approximately 49.6m people) reported using cannabis in the past 12 months.
Professor Yuyan Shi of Herbert Wertheim School of Public Health and Human Longevity Science at the University of California San Diego, the principal investigator of this study, said: “Our findings provide useful information to policymakers and public health practitioners interested in understanding the consequences of legalising recreational cannabis.
“Itʼs especially concerning that increased cannabis use occurs among young people because of the detrimental health effects associated with cannabis use at a young age, including impaired respiratory function, cardiovascular disease and adverse effects on mental health.”
Study details
Recreational cannabis legalisation and transitions in cannabis use: findings from a nationally representative longitudinal cohort in the United States
Christian Gunadi, Bin Zhu, Yuyan Shi.
Published in Addiction on 26 May 2022
Abstract
Aims
This study estimated the likelihoods of individuals transitioning to different cannabis use status following recreational cannabis legalisation (RCL) in the United States.
Design
Secondary analysis of a nationally representative longitudinal cohort in the United States. We used propensity score matching to balance individual characteristics between RCL and comparison states and generalised mixed regressions to estimate behavioural transitions in matched samples.
Participants
A longitudinal cohort of 21 863 individuals (6925 youths and 14 938 adults) participating in the Population Assessment of Tobacco and Health waves 3 and 4.
Setting
Four RCL states that implemented RCL between waves 3 and 4 (California, Massachusetts, Nevada and Maine) and comparison states in the United States.
Measurements
Transitions in cannabis use over the two waves: (1) from non-users to users; (2) from non-users to weekly users; (3) from users to non-users. Individuals in RCL states were compared with matched individuals in (1) states with medical cannabis legalisation (MCL), (2) states not legalising cannabis (non-legalising) and (3) MCL and non-legalising states combined.
Findings
Among youths, the association between RCL and greater odds of transition from non-users to users was seen in comparison with non-legalising states [odds ratio (OR) = 2.18, 95% confidence interval (CI) = 1.37–3.45] and combined states (OR = 1.73, 95% CI = 1.23–2.42). Evidence was lacking regarding the associations between RCL and transitions from non-users to weekly users and from users to non-users. Among adults, RCL was associated with greater odds of transitions from non-users to users and non-users to weekly users if RCL states were compared with non-legalising states (OR = 1.68, 95% CI = 1.15–2.46; OR = 1.82, 95% CI = 1.00–3.31, respectively) or combined states (OR = 1.51, 95% CI = 1.11–2.07; OR = 2.09, 95% CI = 1.19–3.66, respectively). RCL was also associated with lower odds of transition from users to non-users if RCL states were compared with non-legalising states (OR = 0.54, 95% CI = 0.35–0.81).
Conclusions
There appears to be some evidence that recreational cannabis legalisation in the United States is associated with elevated odds of transition to cannabis use among both youths and adults.
See more from MedicalBrief archives:
Cannabis smoking in teenage years linked to adulthood depression
Huge uptick in adolescent cannabis vaping – Columbia study
Canada’s legalisation of cannabis is a success story, despite a shaky first act
Luxembourg first in Europe to legalise cannabis; Canada sees mostly good results
Early cannabis use linked to heart disease – Canadian research