Medical Cannabis May Reduce Some Prescription Drug Use

Medical cannabis may compete with conventional pharmaceuticals in some parts of the health care market, but the research does not show that patients broadly benefit from replacing prescription drugs with cannabis—or that cannabis is generally safer. The evidence points instead to a more cautious conclusion: access to medical cannabis has been associated with lower use of certain medications, while the clinical benefits and risks vary by condition, product, dose and patient.

A 2022 study published in PLOS ONE examined stock-market data from 556 publicly traded pharmaceutical companies around 45 cannabis-legalization events in the United States between 1996 and 2019. The researchers found that pharmaceutical stocks generated returns about 1.5% to 2% lower than expected roughly 10 days after legalization. Using those market changes to estimate future revenue, the authors projected that a single legalization event could be associated with approximately $3 billion in lower annual sales across drugmakers.

That finding is important, but it does not demonstrate that patients stopped taking prescription medicines and switched to cannabis. The study was an event analysis of investor expectations, not a clinical trial or a patient-level study. It included both medical and recreational legalization and covered over-the-counter as well as prescription medicines. Its estimate therefore reflects how investors interpreted legalization—not a direct measurement of improved health outcomes or confirmed drug substitution.

The researchers argued that cannabis could affect several medication markets at once because it is used, legally or otherwise, for a range of conditions. That makes it different from a typical generic drug, which usually competes with a specific brand-name medicine. Still, the breadth of cannabis use should not be confused with proven effectiveness across those conditions.

What prescription-drug studies have found

Earlier research has reported associations between medical-cannabis laws and lower prescription use. In a 2016 Health Affairs study, Ashley Bradford and W. David Bradford analyzed Medicare Part D prescriptions from 2010 through 2013. They found that use of drugs for which cannabis might serve as a clinical alternative declined after states implemented medical-cannabis laws. The analysis included medication categories related to conditions such as pain, nausea, anxiety, depression, seizures, sleep disorders and spasticity.

The study estimated that lower prescription use in states with medical-cannabis laws reduced Medicare spending by about $165 million in 2013. Those results are useful for understanding population-level changes, but they do not establish that every reduction came from a patient replacing a prescription with cannabis. Changes in prescribing practices, eligibility, access to care and other state policies could also have contributed.

Opioid prescribing provides another example. A 2021 study in the Journal of the American Academy of Orthopaedic Surgeons found that state medical-cannabis laws were associated with a 19.7% annual reduction in opioid doses prescribed by orthopedic surgeons to Medicare Part D patients. The association was statistically significant for medical-cannabis laws, particularly laws that permitted dispensaries. The researchers found no significant association between recreational-cannabis legalization and opioid prescribing.

Again, the result should be interpreted carefully. The study used state-level policy and prescribing data rather than randomly assigning patients to cannabis or opioids. It shows that prescribing patterns changed in states with medical-cannabis laws; it does not prove that cannabis caused individual patients to stop using opioids or that cannabis provided equal pain relief.

Cannabis is not automatically safer because it is plant-derived

The original distinction between “natural” cannabis and “synthetic” pharmaceuticals is misleading. Many effective medicines are derived from natural compounds, and plant-based products can also cause side effects, interact with other drugs and vary in strength or purity. Conversely, some cannabinoid medicines are manufactured under pharmaceutical quality controls.

According to the U.S. Food and Drug Administration, the agency has not approved cannabis itself to treat any disease or condition. It has approved specific cannabinoid-related prescription products, including the purified cannabidiol drug Epidiolex for certain seizure disorders and synthetic or synthetic-related products containing dronabinol or nabilone for limited uses such as chemotherapy-related nausea and appetite loss associated with AIDS.

That distinction matters. State medical-cannabis programs generally allow access to products that have not undergone the FDA’s standard review for safety, effectiveness, dosage and manufacturing quality. The composition of dispensary products can vary, and labels may not always accurately reflect cannabinoid content.

What the clinical evidence says

The best-supported uses of cannabinoid medicines are relatively specific. The National Center for Complementary and Integrative Health reports evidence of benefit for some forms of chemotherapy-related nausea and vomiting, appetite loss associated with HIV/AIDS and certain rare seizure disorders. Evidence also suggests modest short-term benefits for some chronic pain and multiple-sclerosis symptoms.

For chronic pain, however, the average benefit appears to be small, and side effects such as dizziness, sleepiness and cognitive impairment are more common than with placebo in many studies. Research on using cannabis to reduce opioid doses has also produced mixed results. Observational studies of state laws cannot substitute for randomized clinical trials that measure pain control, function, quality of life, dependence and long-term safety.

Cannabis also carries risks. THC can impair memory, coordination, judgment and reaction time, and it can make driving dangerous. Cannabis may interact with prescription medicines, and CBD has been linked to sleepiness, gastrointestinal symptoms, liver injury and drug interactions. The Centers for Disease Control and Prevention also notes that cannabis use is not risk-free simply because it is legal under state law.

A possible treatment option—not a universal replacement

Medical-cannabis laws may increase competition in pharmaceutical markets and may be associated with lower use of certain prescriptions, including some opioids. But the available studies do not justify portraying cannabis as a universal substitute for pharmaceuticals or as a treatment with fewer side effects for everyone.

Patients should not stop opioids, antidepressants, sedatives or other prescription medicines abruptly in order to try cannabis. Anyone considering medical cannabis should discuss the decision with a qualified health professional who can review the diagnosis, current medications, potential interactions, product type, dose and applicable state requirements. The most responsible future for cannabis in health care is likely to involve evidence-based use alongside—not automatically instead of—conventional treatment.