Cannabis and Work: Implications, Impairment, and the Need for Further Research

American workplaces are facing unprecedented challenges related to the rapidly evolving landscape of cannabis legalization and its increasing use among workers. Cannabis[1] is the most frequently used illicit drug (by Federal law) among Americans, with an estimated 43.5 million past-year users age 12 or older in 2018 (1). Nearly 18% of adults employed full-time, and nearly 21% of adults employed part-time, reported using cannabis during the previous year. The implications for workplace safety are emerging, as well as concerns about impairment, risk of injury, recruitment and hiring, regulatory issues, and the overall health and well-being of both workers and the public.

Federal and State Status

The Controlled Substances Act administered by the U.S. Drug Enforcement Administration currently classifies marijuana as a Schedule I substance, meaning that it has no accepted medical use and has a high potential for abuse (4). Substances that are classified as Schedule I have the most regulatory restrictions, and thus there are strict limits on researchers’ access to study marijuana and explore its potential medicinal value and public health and safety impacts. Regardless of the federal prohibition of marijuana, 33 states* as well as Washington D.C., Guam, Puerto Rico, and the U.S. Virgin Islands have passed laws legalizing marijuana for medicinal and/or non-medical adult uses at the time of this publication (5).

Work and Safety

While data on marijuana use and workplace safety and health is limited, there is evidence suggesting workplace risks and burdens associated with the drug’s use. Studies of cannabis have demonstrated effects that include sedation, disorientation, impaired judgment, lack of concentration, and slowed fine motor skills, all of which can contribute to delayed decision-making, impaired learning, and memory and attention deficits (6). One such study, reported by the National Institute on Drug Abuse (NIDA), found 55% more industrial accidents, 85% more injuries, and 75% greater absenteeism among employees who tested positive for marijuana compared to those who tested negative (6). Research has also demonstrated a statistically significant association between marijuana use and increased risk of motor vehicle crashes (2,3). The National Safety Council (NSC) released a position statement in 2019 stating that “cannabis impacts psychomotor skills and cognitive ability” and “there is no level of cannabis use that is safe or acceptable for employees who work in safety-sensitive positions” (7). However, not all research is as conclusive about the relationship between marijuana use and occupational injury. A systematic review published in May 2020 found that the current body of literature does not provide sufficient evidence that marijuana users are at increased or decreased risk for occupational injury, and that further high-quality research is needed to eliminate study biases and provide clarity on causality (8).

Impairment

NIOSH recognizes the challenges associated with detecting impairment from marijuana, especially when compared to other substances like alcohol. Impairment from marijuana varies with THC concentration or dose, route of administration, and users’ experience with, or tolerance to, the drug (9). Since marijuana is stored in the fatty tissue, it can be detected through drug testing several days or weeks – long after the individual has stopped experiencing any physiological effects and impaired functioning. The THC levels that create impairment are not well understood and according to the NIDA, there is wide variability in how THC is metabolized by frequent users versus infrequent users which makes interpretation of a positive urine drug test a challenge (10). NIOSH is currently developing information and resources on the topic of impairment testing as a potential adjunct or alternative to certain forms of workplace drug testing. Impairment testing evaluates a worker’s real-time cognitive function and motor skills to determine if there is evidence that the worker may be impaired, regardless of the source of impairment. It is theorized that, compared to traditional workplace drug testing, impairment testing may provide more immediate, actionable, accurate, and comprehensive information, allowing employers to be more proactive in minimizing risks in the workplace while maintaining more privacy and fairness for workers. Research efforts to explore this issue further are of great interest to NIOSH as we develop related content and resources.

Workers’ Compensation

In addition to direct worker safety and health issues, the changing landscape of marijuana legalization and use also has important implications for workers compensation. The impact of marijuana use on workers compensation claims varies from state to state and even organization to organization. NIOSH is exploring workers compensation issues pertaining to marijuana, including but not limited to:

• determination of impairment at the time of an injured worker’s accident;
• impact on a worker’s compensation claim if employee tested positive for state-approved and/or physician-recommended medical marijuana at the time of an accident; and
• potential for reimbursement for medical marijuana used to treat a work-related injury.

According to the National Council on Compensation Insurance (NCCI), most jurisdictions have workers compensation laws that, in some form, restrict workers compensation benefits when the injury is attributed to intoxication or drug use (11). Interestingly, some research suggests that medical marijuana could have a positive impact on worker safety and health. Medical marijuana may allow workers to better manage pain and other symptoms associated with workplace injuries and illnesses, reducing worker’s compensation claims (12) and the use of opioids (13-15). However, further research, including more comprehensive and long-term studies, are needed to better understand these relationships.

Knowledge Gaps

Despite the evolving landscape of legalization and commercialization, there are gaps in the knowledge guiding workplace policies surrounding marijuana, including those related to worker safety and health and privacy and confidentiality issues. We must work to address research barriers, fill research gaps, and improve research quality and surveillance capacity. Research on the association between cannabis use and occupational safety and health needs to be explored across different populations, occupations, workplace settings, worker characteristics, and work patterns. Research should also focus on understudied demographics, including working adolescents and employed older populations. Similarly, the evolution of marijuana legalization and use presents several critical considerations for employers, including, but not limited to:

• comprehensive impairment policies and testing methodology;
• state antidiscrimination or reasonable accommodation provisions for state-approved medical marijuana;
• awareness and delegation of safety-sensitive roles and tasks; and
• employer liability.

NIOSH will also continue to conduct research and Health Hazard Evaluations (HHEs) specific to worker safety and health in the rapidly expanding marijuana production and retail industry sectors.

Future

Like any emerging hazard with worker and workplace implications, the rise in marijuana use among workers deserves critical review, additional research and a deeper understanding. It is vital to examine this issue through the lens of occupational safety and health, and to prepare for the inevitable and continuous changes to come. NIOSH is taking crucial first steps in examining this topic and welcomes input and recommendations from its stakeholders.

John Howard, MD, is the Director of the National Institute for Occupational Safety and Health (NIOSH).

L. Casey Chosewood, MD, is the Director of the NIOSH Office for Total Worker Health®.

Lore Jackson-Lee, MPH, is the Associate Director for Policy, Planning, and Evaluation at NIOSH.

Jamie Osborne, MPH, CHES® is a Public Health Analyst with the NIOSH Office of Policy, Planning, and Evaluation.

*error corrected 6/23/2020 (changed 34 to 33 states)

References

1. 2018 NSDUH Annual National Report https://www.samhsa.gov/data/release/2018-national-survey-drug-use-and-health-nsduh-releases
2. The Health Effects of Cannabis and Cannabinoids https://www.nap.edu/catalog/24625/the-health-effects-of-cannabis-and-cannabinoids-the-current-state
3. Marijuana and Public Health https://www.cdc.gov/marijuana/nas/index.html
4. 21 U.S.C. Chap 13, § 801 et seq. at https://www.dea.gov/controlled-substances-act
5. State Medical Marijuana Laws https://www.ncsl.org/research/health/state-medical-marijuana-laws.aspx
6. NIDA Report: Marijuana https://www.drugabuse.gov/publications/research-reports/marijuana
7. NSC Policy/Position Statement: Cannabis Impairment in Safety Sensitive Positions https://www.nsc.org/Portals/0/Documents/NSCDocuments_Corporate/Policy-Positions/Workplace/W-Cannabis%20Impairment%20in%20Safety%20Sensitive%20Positions%20-%20153.pdf?utm_source=hs_email&utm_medium=email&utm_content=78251464&_hsenc=p2ANqtz-_gU9WkxfUFUlEJK1cj1GlUDuzdoYvLqJGF79Cj_7cwH66AWvQogXE3ieZm0R1WvoOiK94Im0-X98M-scT-GKtb92tjIg&_hsmi=78251464
8. Wade R. Biasutti, Kurt S. H. Leffers & Russell C. Callaghan (2020): Systematic Review of Cannabis Use and Risk of Occupational Injury, Substance Use & Misuse, DOI: 10.1080/10826084.2020.1759643
9. Phillips, J. A., Holland, M. G., Baldwin, D. D., Gifford-Meuleveld, L., Mueller, K. L., Perkison, B., … Dreger, M. (2015). Marijuana in the Workplace: Guidance for Occupational Health Professionals and Employers: Joint Guidance Statement of the American Association of Occupational Health Nurses and the American College of Occupational and Environmental Medicine. Workplace Health & Safety, 63(4), 139–164. https://doi.org/10.1177/2165079915581983
10. NIDA News Release: Research on THC blood levels sheds light on difficulties of testing for impaired driving https://www.drugabuse.gov/news-events/news-releases/2016/01/research-thc-blood-levels-sheds-light-difficulties-testing-impaired-driving
11. National Council on Compensation Insurance https://www.ncci.com/Articles/Pages/II_Marijuana-Conversation-Employer.aspx#
12. Ghimire KM, Maclean JC. Medical marijuana and workers’ compensation claiming. Health Economics. 2020;1–16. https://doi.org/10.1002/hec.3992
13. Bradford AC and Bradford WD. 2016. “Medical Marijuana Laws Reduce Prescription Medication Use in Medicare Part D,” Health Affairs 35, no. 7 (2016): 1230–1236.
14. Bradford AC, Bradford WD, Abraham A, Bagwell Adams G. Association Between US State Medical Cannabis Laws and Opioid Prescribing in the Medicare Part D Population. JAMA Intern Med. 2018;178(5):667–672.
15. Wen H, Hockenberry JM. Association of Medical and Adult-Use Marijuana Laws with Opioid Prescribing for Medicaid Enrollees. JAMA Intern Med. 2018;178(5):673–679.

[1] The terminology used to describe the cannabis plant, its components, and the physiological impacts of the different compounds in the plant are complex and contribute to much of the confusion surrounding it. Cannabinoids refer to the many chemical compounds unique to the cannabis sativa plant. Delta-9-tetrahydrocannabinol, or THC, is the main psychoactive cannabinoid, which gives users the “high” associated with the plant, and cannabidiol, or CBD, is the main non-psychoactive cannabinoid. Cannabis sativa that has high levels of THC and lower levels of CBD is referred to as “marijuana” (2,3). In this blog, marijuana will be used to refer to the Cannabis plant and to the THC-containing drug made from the plant.