The research team, led by Zachary L. Mannes of Columbia University Irving Medical Center and Deborah S. Hasin of Columbia University and the New York State Psychiatric Institute, focused on VHA patients aged 18 to 75 with chronic pain diagnoses. Veterans are a population of particular interest in this debate because chronic pain is among the most common conditions treated in the VA system, and the department has spent more than a decade working to reduce opioid exposure among its enrollees. The VA reports having cut the number of veterans prescribed opioids dramatically since 2012, through initiatives such as the Opioid Safety Initiative and updated clinical practice guidelines that emphasize non-opioid pain management. Against that backdrop, any independent effect of state cannabis policy is difficult to detect, which makes the new study’s methods especially important.

To isolate the effect of legalization from these broader secular trends, the investigators used staggered-adoption difference-in-difference models, a technique that has become the workhorse of modern policy evaluation. Because different states legalized medical cannabis and recreational cannabis at different times, the researchers could compare prescribing outcomes within the same patients and states before and after each law took effect, using states without such laws as the comparison group. States were categorized each year as having no medical or recreational cannabis law, a medical cannabis law only, or both. This approach controls for fixed characteristics of states and for national trends in opioid prescribing, such as the prescribing declines that followed the 2016 CDC opioid guideline, leaving the change associated with legalization itself.

The outcomes the team tracked were carefully chosen to capture different dimensions of opioid risk. They examined whether patients received at least 30 days of prescription opioids, whether they were on long-term opioid therapy, defined as at least 90 consecutive days of opioid supply without a gap of more than 15 days, whether they received high-dose opioids of at least 50 morphine milligram equivalents per day, and whether opioids were co-prescribed with benzodiazepines, a combination strongly linked to overdose death. Each of these measures reflects a distinct clinical decision point, from initiating an opioid prescription to escalating dose or layering on a sedative, and each has been flagged in national guidelines as a marker of potentially hazardous prescribing.

The results paint a nuanced picture. Enactment of a medical cannabis law was associated with a reduction of 0.79 percentage points in the share of patients receiving at least 30 days of opioids, and a reduction of 0.34 percentage points in long-term opioid therapy, relative to states without such laws. Those numbers may sound small, but applied across the enormous VHA population with chronic pain, they translate into thousands of patients shifting away from extended opioid courses. Notably, however, medical cannabis laws were associated with slight increases in the other two risk markers: high-dose opioid prescribing rose by 0.09 percentage points and opioid-benzodiazepine co-prescribing rose by 0.11 percentage points, changes the authors interpret cautiously given their small magnitude.

The story changed when recreational cannabis laws entered the picture. Following the enactment of recreational legalization, on top of existing medical laws, the researchers observed further declines in at least 30-day opioid prescribing, with an additional reduction of 0.14 percentage points, and more substantial drops in the two high-risk markers. High-dose opioid prescribing fell by 0.33 percentage points and opioid-benzodiazepine co-prescribing fell by 0.33 percentage points compared with the period after medical legalization alone. In other words, the transition from medical-only to full legalization was associated not just with less opioid prescribing overall, but with less of the kind of prescribing most closely tied to overdose risk, a pattern that runs counter to fears that wider cannabis availability would compound dangerous drug combinations.

Age emerged as a critical modifier of these effects. The associations between cannabis laws and opioid prescribing were generally more consistent among adults aged 65 to 75, the oldest group in the cohort. This finding is striking given that cannabis use has been rising fastest among older Americans in recent years, and given that older adults face elevated risks from both opioids and benzodiazepines due to altered drug metabolism, falls, and respiratory depression. If legal cannabis access is substituting for opioids anywhere, the data suggest it may be among older veterans with chronic pain, a group in whom clinicians may be particularly motivated to taper high-risk regimens when an alternative becomes legally available.

The authors are careful about what these associations do and do not mean. Difference-in-difference estimates capture population-level changes in prescribing, not individual decisions, and the study cannot confirm that any specific patient replaced an opioid with cannabis. The plausible mechanism, the researchers suggest, involves changes in both patient and clinician treatment decisions: patients in legal states may request cannabis as part of their pain management, and clinicians may feel more comfortable tapering opioids when patients have a sanctioned alternative. Survey evidence has long shown that chronic pain is the leading qualifying condition for medical cannabis licenses, and prior studies in Medicare and Medicaid populations have reported similar directional findings, though the literature overall has been mixed, with some studies finding no effect or effects concentrated in specific subgroups.

The study also arrives amid ongoing scientific uncertainty about whether cannabis actually relieves chronic pain. Randomized trials and meta-analyses of cannabinoids for chronic non-cancer pain have produced modest and inconsistent evidence of benefit, and recent best-practice advice from the American College of Physicians acknowledges both the limited efficacy data and the potential harms of cannabis use. Previous work by some of the same researchers found that cannabis legalization was associated with increases in cannabis use disorder diagnoses among VHA patients with chronic pain, a reminder that expanded access carries its own risks. The new findings therefore do not settle whether cannabis is an effective analgesic; they document a shift in prescribing behavior that accompanies legalization, whatever its underlying cause.

What the study does offer is the most comprehensive picture to date of how cannabis policy intersects with opioid care in the largest integrated health system in the United States. By following VHA patients through a decade in which the legal landscape transformed state by state, and by separating medical from recreational laws and dissecting prescribing into clinically meaningful risk categories, the research moves the debate beyond anecdote. The message for policymakers is measured: greater legal cannabis access appears associated with modest reductions in opioid prescriptions for chronic pain, particularly long-term therapy and, after recreational legalization, high-risk prescribing patterns, while the clinical question of whether cannabis should be recommended for pain remains open. As more states reconsider their cannabis laws, studies like this one will be essential for weighing the trade-offs embedded in those decisions.

Subject of Research: Association between state cannabis legalization and opioid prescribing patterns among veterans with chronic pain

Article Title: Cannabis Legalization and Opioid Prescribing in Veterans Health Administration Patients: 2013–2022

Article References: Mannes, Z. L., Wall, M. M., Stohl, M., Malte, C. A., Olfson, M., Livne, O., Fink, D. S., Simpson, T., Wisell, C. G., Keyhani, S., Martins, S. S., Cerdá, M., Sacco, D. L., Gutkind, S., Maynard, C. C., Sherman, S., Saxon, A. J., & Hasin, D. S. (2026). Cannabis Legalization and Opioid Prescribing in Veterans Health Administration Patients: 2013–2022. Journal of General Internal Medicine. https://doi.org/10.1007/s11606-026-10733-8

Image Credits: AI Generated

DOI: 10.1007/s11606-026-10733-8

Keywords: cannabis legalization, opioid prescribing, chronic pain, Veterans Health Administration, medical cannabis law, recreational cannabis law, long-term opioid therapy, benzodiazepine co-prescribing, difference-in-difference, older adults, pain management, public health policy