The greatly increased availability of cannabis over the last two decades has outpaced our understanding of the public-health impacts of the drug. It is now available for medical purposes in most states, and adults may now purchase it for recreational use in nearly half the states. With greater availability has come decreased public perception of harm, as well as increased use.
In this uncertain and rapidly changing landscape, research on cannabis and cannabis policy is badly needed to guide individual and public health decision-making.
The National Survey on Drug Use and Health reported that between 2012 and 2019, past-year use of cannabis among people 12 and older rose from 11 percent to over 17 percent, and although trend comparisons aren’t possible because of changes in the survey’s methodology, in 2022, nearly 22 percent of people had used the drug in the past year. Very steep increases are also being seen in the number of people 65 and older who use cannabis.
At the same time, the cannabis industry is producing an ever-wider array of products with varying and sometimes very high concentrations of delta-9-tetrahydrocannabinol (THC) Greater harms from cannabis use are associated with regular consumption of high-THC doses. And there is a cornucopia of other intoxicating products available to the public, some containing other cannabinoids about which we still know very little.
To create a roadmap for research in this space, NIDA along with the National Center for Complementary and Integrative Health (NCCIH), the National Cancer Institute (NCI), and the Centers for Disease Control and Prevention (CDC), sponsored an independent consensus study by the National Academies of Sciences, Engineering, and Medicine (NASEM). The study resulted in a comprehensive report, Public Health Consequences of Changes in the Cannabis Policy Landscape, that was published in September.
The report describes in detail the different regulatory frameworks that exist in different states, and it draws on prior research to identify policies that are likeliest to have the greatest impact protecting public health. Those include approaches like restrictions on retail sales, pricing, and marketing; putting limits or caps on THC content in products; and laws about cannabis-impaired driving. They also could include different forms of taxation and even state monopolies. While state monopolies have not yet been tried with cannabis, they have proven effective at reducing the public health impacts of alcohol.
But the report also underscores that few conclusions can yet be drawn about the impacts of legalization or the different ways it been implemented. It is clear that people are consuming cannabis more and in a wider variety of ways, and there is some evidence of increases in emergency department visits due to accidental ingestion, car accidents, psychotic reactions, and a condition of repeated and severe vomiting (hyperemesis syndrome). But we are hindered in our further understanding because policy details vary so much between states and because data are collected and reported in so many different ways, making interpretation difficult.
Consequently, the report enumerates recommendations for research that should be conducted by federal, state, and tribal agencies to provide greater clarity and inform policy, including several domains within the purview of the NIH.
The report underscores the need for more detailed information on health and safety outcomes associated with specific policy frameworks. This includes more data on outcomes associated with different regulations for how cannabis products are sold and marketed, whether they can be used in public spaces, and whether more restrictive rules about how cannabis can be sold, such as those existing in other countries like Uruguay, are associated with improved health and safety outcomes. Many states have developed approaches to promote health and social equity, including programs to expunge or seal records of cannabis offenses and preferential licensing for individuals or groups most adversely impacted by the disparities in criminal penalties, but whether these programs will achieve their intended goals also requires careful evaluation.
Finally, more research is needed on the health effects of cannabis use by specific groups like youth, pregnant women, older adults, and veterans, and on its effects in individuals with various medical conditions for which medicinal cannabis might be used. Studies are also needed on health effects of the high-potency and synthetic or semi-synthetic cannabinoid products that are emerging. But the authors underscore that the focus cannot solely be that of risks—it must also include research on potential benefits of cannabis in managing some chronic mental or physical health conditions as well as interactions with prescription drugs that patients may already be taking to manage their health issues.
Much of this research will require or benefit from better surveillance of cannabis cultivation, product sales, and patterns of use. Existing surveillance, as the report points out, has suffered from a lack of funding and coordination, producing gaps in our knowledge. There is also a need for better tests for detecting cannabis impairment. Unlike alcohol, THC remains in the body long after its psychoactive effects have worn off. So, unlike commonly used alcohol sobriety tests, blood tests for cannabis that are currently widely used in law enforcement and employment screening cannot distinguish between recent or past use. Better surveillance and improved tests can inform research on interventions to mitigate risks to health and safety associated with cannabis use. They can also help inform the development of cannabis product safety and quality standards.
Some of the pressing questions identified by the NASEM report are already research priority areas for NIDA. For instance, our medicinal cannabis registry, which was funded starting in 2023, will be able to inform research, policy, and practice by gathering longitudinal data about cannabis use and outcomes from a cohort of people using the drug medicinally. The project will include a program to test the composition and potency of cannabis products used and will integrate registry data with other data sources.
The NIDA-funded Monitoring the Future survey has tracked nationwide cannabis use trends in adolescents and young adults for decades. The survey has recently recorded reduction in teenage use of substances in general, including cannabis, and recent surveys have also shown increases in disapproval of cannabis use and perception of its harms in this age group. However, it continues to show that cannabis is one of the most-used drugs by teenagers, with a quarter of 12th graders reporting use in the past year.
Since its launch nearly a decade ago, the trans-NIH Adolescent Brain Cognitive Development (ABCD) study has been collecting longitudinal data on drug use and its developmental impacts in a large national cohort from late childhood through early adulthood. More recently, ABCD has been complemented by a similar study on the first decade of life, the multi-Institute Healthy Brain and Child Development (HBCD) study. HBCD is recruiting a cohort of pregnant participants across the country and will use neuroimaging and other tools to track the impacts of prenatal exposure to cannabis and other environmental influences on the developing brain. By identifying risk and resilience factors for cannabis use in youth, the data from ABCD and HBCD will be extremely valuable in informing prevention programs in these age groups.
Advances in cannabis and cannabis policy research could be aided by wider adoption of the standard 5mg unit of THC required in research studies funded by NIDA and other NIH Institutes. Adoption of this standard was based on the need for consistency across research studies, which will facilitate more real-world-relevant research and translation of findings into policy and clinical practice. Research using this standard could also provide better insights into the effects of cumulative exposure and long-term developmental and cognitive effects of prenatal exposure.
Scientific research should always drive best practices in public health. To that end, NIDA and other NIH institutes will continue to support essential research on cannabis, the health effects of new products, and the effects of policy changes around this drug. It is essential to ensure that, where they are legal, product contents are accurately represented to the consumer in an environment where public health takes precedence over profits.
Dr. Nora Volkow, Director
Here I highlight important work being done at NIDA and other news related to the science of drug use and addiction.
