The United States has a complicated relationship with cannabis and its legal status, particularly with high levels of tension between the state and federal levels (Young-Wolff et al., 2022). At the federal level, cannabis is classified as a controlled substance under the Controlled Substances Act (1906). This means that it is officially considered to have a high potential for abuse and is not a recognized medical treatment option for any disease or condition by the United States Food and Drug Administration.
Despite federal classification, there has been a move toward decriminalization at the state level with many states enacting medical marijuana laws (MCLs) and recreational marijuana laws (RCLs) (Martins et al., 2016). For MCL in most states, they require patients to get a doctor's referral and may need to register with a state program. However, most RCLs require an individual to be over 21 and have ID, and they can then purchase cannabis from a large number of licensed dispensaries.
Military veterans face unique stressors not faced by their civilian counterparts, such as trauma, frequent self- and/or family relocation, long-term deployments, and prevalence of mental health and physical health disorders (Inoue et al., 2023). It is an area of growing concern chronic pain. Research has shown that some veterans report experiencing pain, and many describe it as severe (Nahin, 2016). Causes vary, but can include combat-related injuries, training injuries, and wear and tear from hard military service.
Chronic pain can affect daily functioning, quality of life, and is associated with depression, substance use, and sleep disturbances. Some veterans have turned to cannabis to moderate and mediate pain symptoms and improve quality of life.
Therefore, Hasin and colleagues (2023) aimed to investigate whether medical or recreational marijuana legalization had any effect on the increase in cannabis-related problems and long-term pain among US veterans using Veterans Health Administration (VHA) services.
Chronic pain and cannabis use are prevalent among US veterans.
Methods
The authors reviewed the health records of patients who sought primary care, emergency care, or mental health services administered by the US Veterans Health Administration (VHA) between 2005 and 2019. acceptance. The sample was then divided into two groups: those with and without long-term pain using the American Pain Society's taxonomy of painful medical conditions.
For each group, patients with clinically diagnosed cannabis use disorder were identified based on ICD-9-CM or ICD-10-CM clinical codes. 'CM' refers to the clinical modification, which is a modified version of the International Classification of Diseases for use in the US only. Importantly, patients were excluded if they were in remission or had no cannabis use disorder code defined.
The sample was analyzed using linear binomial regression models stratified by pain and time-varying state-level legal status. This changing situation over time was based on the legalization of cannabis for medical use in every state. In addition, patient covariates such as age, sex, race, and ethnicity were also used to adjust the models.
Results
In total, 15 cross-sectional annual datasets representing each year between 2005 and 2019 were analyzed. This was between 3,234,383 and 4,579,994 patients depending on the year. The main findings of the study were:
- Among patients without chronic pain in 2005, 5.1% were women with a mean age of 58.3 years. The ethnic breakdown was 75.7% white, 15.6% black, and 3.6% Hispanic or Latino. By 2019, the percentage of female patients increased to 9.3% with an average age of 56.7 years. The ethnic breakdown changed to 68.1% white, 18.2% black, and 6.5% Hispanic or Latino.
- Focusing on those with chronic pain, 7.1% were women with a mean age of 57.2. The ethnic breakdown was 74% white, 17.8% black, and 3.9% Hispanic or Latino. By 2019, the percentage of female patients increased to 12.4%, and the average age remained at 57.2 years. The ethnic distribution changed to 65.3% white, 21.9% black, and 7.0% Hispanic or Latino.
- In patients with chronic pain, there was a 0.135% (95% CI 0.118 to 0.153) increase in the prevalence of cannabis use disorders since the introduction of medical cannabis laws (MCL).
- Since the introduction of recreational cannabis laws (RCL), there has been a 0.188% (95% CI 0.160 to 0.217) increase in the prevalence of cannabis use disorders.
- Interestingly, in patients without chronic pain, there were smaller increases in the prevalence of cannabis use disorders after applying the MCL and RCL (MCL: 0·037% (0.027 to 0.048), 5.7%
Overall, Hasin and colleagues (2023) found that the association of MCL and RCL with cannabis use disorder was greater in patients with chronic pain than those without. However, the observed increase was only a fraction of a percentage point.
US veterans with chronic pain were more likely to use cannabis for medical and recreational purposes.
Results
Hasin and colleagues (2023) found a significant increase in cannabis use disorder due to the administration of MCL and RCL in those with chronic pain. The authors also noted significant increases in cannabis use disorder in older age groups following the introduction of these laws. This led the authors to conclude that MCL and RCL could increase the prevalence of cannabis use disorder, and their commercialization resulted in improved access.
The introduction of medical and recreational cannabis laws has resulted in increased use of cannabis use disorder for those with chronic pain.
Strengths and limitations
This study had several strengths. Of note, this is the first study to examine differences in the relationship between MCL, RCL, and impact on cannabis use disorder prevalence in the context of a chronic pain condition. The study examined a large cross-sectional cohort with data collected over a 15-year longitudinal period. This meant that incremental changes over time could be assessed. Overall, the study is an important addition to the evidence base regarding older patients with chronic pain and the increased use of cannabis.
The current paper has several limitations. Because the majority of patients at the VHA are predominantly White, male, and between the ages of 65 and 75, they are not representative of veterans or the general population. Sample characteristics may limit the generalizability of findings more broadly. Additionally, there was a high bar for cannabis use disorder diagnoses. This is because diagnoses are made by clinicians who diagnose most severe disorders and may otherwise have missed subclinical cases obtained with sensitive structured assessments. In addition, the lag effect of the implementation of the law should be taken into account, since the effect of such laws takes a long time to emerge. The authors analyzed time lags of 1 year to ensure that as many RCL states were included in the analysis as possible, since for many these were implemented in recent years. As time progresses and more information becomes available, longer time lags should be analyzed to examine the lagged effects of the impact of law changes.
This study used a large electronic health record database of more than 3 million US veterans.
Implications for practice
This study has major implications for policy, clinical care, and research. The authors demonstrated that the prevalence of cannabis use disorder is disproportionately increased with chronic pain, particularly among older adults under state law. Thus, reducing the risk of harm related to this public health problem is important, but proportionate to other health needs.
It is suggested that elderly patients with chronic pain who use cannabis should be closely monitored by their treating clinicians and informed of the risks of cannabis use disorder and alternative treatments. This is especially true for patients who live in states where cannabis use has been legalized and who may be more vulnerable to cannabis use disorder. In the context of the UK, medical cannabis was legalized under specific circumstances in 2018, but there is still no work to examine the impact of this legalisation. This may be a unique opportunity to explore implications for future practice.
Research should monitor the short-term and long-term harms associated with cannabis use disorder, particularly in patients with comorbidities such as chronic pain. This should be communicated to policy makers, clinicians and the general public to provide unbiased scientific evidence that does not compete with public health and commercial interests.
In the United States, cannabis is a multi-billion dollar industry with increasingly positive public beliefs about its safety and efficacy. Often, companies that distribute medicinal cannabis advertise unsubstantiated claims about the safety and efficacy of their products, creating more demand. Public health campaigns that address the risk and associated harms of cannabis use disorder in those with chronic pain are needed.
Clinicians supporting chronic pain patients who use cannabis should increase awareness of and closely monitor the risks of cannabis use disorder.
Statement of interest
Grace Williamson and Daniel Leightley are currently conducting a study with the University of Southern California and the RAND Corporation examining cannabis use in association with PTSD symptoms in the United States and the United Kingdom. In addition, Daniel Leightley is an army reservist in the United Kingdom Armed Forces and this review was carried out as part of his civilian work.
Connections
Primary paper
S. Hasin et al., “Chronic pain, cannabis legalization, and cannabis use disorder among patients in the US Veterans Health Administration system, 2005–2019: a retrospective, cross-sectional study,” The Lancet Psychiatry , vol. 10, no. 11, p. 877–886, November 2023, doi: 10.1016/S2215-0366(23)00268-7.
Other references
KC Young-Wolff, RL Pacula, and LD Silver, “California Cannabis Markets – Why Industry-Friendly Regulation Is Not Good for Public Health,” JAMA Heal. Forum, vol. 3, no. 7, p. e222018, July 2022, doi: 10.1001/jamahealthforum.2022.2018.
Controlled Substances Act. 1906.
SS Martins and b.“State-level medical marijuana laws, marijuana use, and marijuana availability in the general US population,” Drug Addiction to Alcohol., vol. 169, p. 26–32, December 2016, doi: 10.1016/j.drugalcdep.2016.10.004.
J. Inoue, E. Shawler, CH Jordan, MJ Moore, and CA Jackson, Veteran and Military Mental Health Issues. 2023.
RL Nahin, “Severe pain in veterans: effects of age and gender and comparisons with the general population,” J. Pain, vol. 18, no. 3, p. 247–254, March 2017, doi: 10.1016/j.jpain.2016.10.021.