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Research Highlight

Cannabis Use Among Veterans: Research Needs Come into Focus

Cannabis is one of the most commonly consumed psychoactive drugs in the United States, and use among adults has steadily increased over the past decade. According to data from the National Survey on Drug Use and Health (NSDUH), the percentage of adults ages 18-25 who reported past-year (i.e., recent) cannabis use rose from 27.8 percent in 2008 to 34.8 percent in 2018.¹ The corresponding estimate among adults ages 26 or older nearly doubled over the same period, from 7.0 percent to 13.3 percent. These documented increases coincide with the growing acceptability of and access to cannabis across the country. Although cannabis remains a Schedule I controlled substance and illegal under U.S. federal law, 33 states and the District of Columbia (D.C.) have legalized cannabis use for those with qualifying medical conditions, beginning with California in 1996. In addition, 11 states and D.C. have legalized recreational cannabis use.

Compared with the U.S. civilian population, relatively little is known about cannabis use and health outcomes among U.S. Veterans. In 2018, Davis et al. published one of the first nationally-representative studies examining the prevalence and correlates of recent recreational and medical cannabis use among U.S. Veterans.² The authors found that approximately 1 in 11 (~9 percent) U.S. Veterans used cannabis in the past year. Further, in states where medical cannabis was legal, nearly 41 percent of the Veterans who used cannabis in the past year reported medical use. Compared with findings from general U.S. population-based studies, the prevalence of recent cannabis use was similar or slightly lower among Veterans; however, among those with past-year use, the percentage of Veterans using medically was more than double that of the general population, highlighting the salience of medical use among Veterans.

In states with medical cannabis laws, many of the qualifying conditions for medical use (e.g., chronic pain and posttraumatic stress disorder [PTSD]) are particularly relevant to Veteran populations. Although there is potential for some individuals with these conditions to derive therapeutic benefit from cannabis, empirical evidence regarding such benefit is largely unavailable, of low quality, or inconclusive at this time. Additional rigorous and longer-term studies are needed in this topic area. Conversely, the negative consequences associated with cannabis use are relatively well-documented. Consistent evidence links frequent or heavy cannabis use with an increased risk for several adverse health and psychosocial outcomes, including psychosis, chronic bronchitis, lower life satisfaction and achievement, and the psychiatric syndrome of cannabis use disorder.³ Such harms associated with use may be even more pronounced among certain population subgroups with preexisting physical and mental health conditions, which tend to be overrepresented among Veterans Health Administration (VHA) patients, and using cannabis may negatively affect the course of illness and treatment outcomes in these subgroups. Nonetheless, it is important to note that the evidence base regarding adverse consequences associated with cannabis use has generally not distinguished between non-medical and medical use or has exclusively examined recreational use. Consequently, there is a need for further research that studies the potential harms associated with medical versus non-medical cannabis use.

In addition to examining the average harms and benefits of use, it is vital to study the demographic, substance use, and health correlates and outcomes of both non-medical and medical cannabis use among Veterans using VHA services. One of the very few published studies on this topic found that cannabis use disorder diagnoses among VHA patients increased by about 50 percent from 2002 to 2009 (from 0.66 percent to 1.05 percent).⁴ Moreover, the percentage of patients with diagnosed cannabis use disorder was greater in states with medical cannabis laws than in states without such laws during this time period. The study also identified greater psychiatric comorbidity, including PTSD, among patients with cannabis use disorder as compared to those with another diagnosed substance use disorder. Additional research is required to better understand the implications for the broader spectrum of cannabis-using patients (not only those diagnosed with a cannabis use disorder in VHA), including the relationship between level of cannabis use and physical health, mental health, and other health services outcomes. 

The relatively large and growing number of Veterans using cannabis has important potential implications for Veteran health and the VHA system. We have an ongoing project to characterize and understand patterns of cannabis use and how they relate to health, functioning, and service utilization among VHA primary care patients. Our study screens Veterans receiving primary care at three VA Medical Centers in the Midwest to identify a large cohort of patients with regular cannabis use. Eligible patients who enroll in the cohort complete in-depth assessments at baseline and at 6- and 12-month intervals to identify cannabis use and cannabis use disorder symptom trajectories, as well as other health, functioning, and service utilization outcomes. Findings from this study will have important implications for VHA patients, providers, and policymakers. More broadly, this work, combined with expanded data on Veteran cannabis use from other sources, is needed to better understand the potential consequences of medical and non-medical cannabis use among Veterans, identify patients for whom additional services may be indicated to address cannabis use, and inform VHA clinical practice guidelines regarding cannabis use.

References

1. Substance Abuse and Mental Health Services Administration Key Substance Use and Mental Health Indicators in the United States: Results from the 2018 National Survey on Drug Use and Health.” HHS Publication No. PEP19- 5068, NSDUH Series H-54, 2019. Rockville, MD: Center for Behavioral Health Statistics and Quality, Substance Abuse and Mental Health Services Administration.
2. Davis AK, Lin LA, Ilgen MA, Bohnert “Recent Cannabis Use Among Veterans in the United States: Results from a National Sample,” Addictive Behaviors 2018; 76:223-28.
3. Volkow ND, Baler RD, Compton WM, Weiss “Adverse Health Effects of Marijuana Use,” New England Journal of Medicine 2014; 370(23):2219-27.
4. Bonn-Miller MO, Harris AHS, Trafton “Prevalence of Cannabis Use Disorder Diagnoses Among Veterans in 2002, 2008, and 2009,” Psychological Services 2012; 9(4):404-16.