A major review found that US adults increasingly view cannabis as harmless while evidence shows national increases in cannabis potency, prenatal exposure, unintentional childhood exposure, adult use, cannabis use disorders, ER visits, and fatal vehicle crashes.
Read this if you want a comprehensive overview of cannabis trends, risks, and legal impacts in the United States.
MMLs did not increase teen use but increased adult use, potency, and cannabis disorders
What the researchers found
This comprehensive review documented the shifting landscape of cannabis use in the United States.
Both adults and adolescents increasingly perceive cannabis as harmless. Meanwhile, the evidence showed national increases in cannabis potency, prenatal and unintentional childhood exposure, adult cannabis use, cannabis use disorders, cannabis-related emergency room visits, and fatal vehicle crashes involving cannabis.
Regarding medical marijuana laws (MMLs): many studies indicated that MMLs did not increase adolescent cannabis use. However, MMLs appeared to increase cannabis potency, unintentional childhood exposures, adult cannabis use, and adult cannabis use disorders.
An intriguing ecological finding: MMLs appeared associated with substitution of cannabis for opioids, and possibly for psychiatric medications.
The review noted that some people can use cannabis without harm, but potential problems include prenatal exposure effects, decline in educational or occupational functioning after early adolescent use, impaired driving, cannabis use disorders, cannabis withdrawal, and psychiatric comorbidity.
Why it matters
This review by a leading epidemiologist provides a single-source overview of US cannabis trends during a period of rapid legal change. The finding that perception of harmlessness is increasing while measurable harms are also increasing highlights a growing disconnect between public attitudes and public health data.
The numbers in context
29 states had medical marijuana laws, 8 had recreational marijuana laws at time of review. National increases documented in: cannabis potency, use, use disorders, ER visits, fatal vehicle crashes. MMLs did not increase adolescent use but did increase adult use and disorders.
How the study worked
Comprehensive narrative review of US epidemiological data, published studies, and trend analyses on cannabis use patterns, associated problems, and the impact of medical and recreational marijuana laws.
What this study cannot tell us
As a narrative review, it synthesizes selectively rather than systematically. Many of the trends documented are ecological associations that cannot prove causation. The landscape of cannabis laws changes rapidly, potentially outdating specific findings. Individual-level data on causation between MMLs and behavior change is limited.
How to read the evidence
Published in Neuropsychopharmacology by a leading epidemiologist, this comprehensive review draws on strong epidemiological data and national surveys.
When this study was published
Published in 2018. Many more states have adopted recreational marijuana laws since, and trends have continued to evolve.
The bigger picture
The opioid substitution finding is particularly significant. If medical marijuana access leads some people to substitute cannabis for opioids, the net public health effect could be positive despite the increases in cannabis-specific harms. This tradeoff is central to the policy debate.
Questions still open
- Will recreational marijuana laws accelerate the trends documented for medical marijuana laws? Is the cannabis-for-opioid substitution effect large enough to offset increased cannabis harms? How should public health messaging address the growing perception of harmlessness?
Common questions
Did medical marijuana laws increase teen cannabis use?
Is cannabis getting more dangerous?
Read the original research
US Epidemiology of Cannabis Use and Associated Problems.
Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 43(1), 195-212
Citation
Hasin, Deborah S. (2018). US Epidemiology of Cannabis Use and Associated Problems.. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 43(1), 195-212. https://doi.org/10.1038/npp.2017.198
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