As medical cannabis use explodes, evidence behind it thins

Clinical takeaway: Patients are increasingly obtaining cannabis to treat anxiety and PTSD, conditions where supporting data remain limited. Expect these conversations and be ready to counsel based on the evidence. 

Medical cannabis puts clinicians in an odd position. Products are now legal in 41 states and the District of Columbia, and this April federal law reclassified them from Schedule I to Schedule III. Yet nothing sold at a dispensary carries an FDA approval so clinicians can't prescribe, while patients obtain licenses to buy from state-licensed retailers or turn to caregivers. 

In states with medical programs, patients enroll in a registry with a clinician-certified qualifying condition, and the state logs who holds a card and why. Those registries have been the main window into national use, though an imperfect one. California's is voluntary, and states report with varying consistency. Two registry analyses track medical registrations and qualifying conditions across nine years, as well as data on authorizing clinicians and accessing caregivers. 

Registered patients climbed to 3.9 million in 2024, up from about 747,000 in 2016, a 425% increase. The population rate rose to 195.9 per 10,000 people, up from 70.9. Growth flattened after 2022 with enrollment falling in 15 of 19 jurisdictions once recreational dispensaries opened, a pattern the authors ascribe to patients meeting medical needs through recreational products without licensure. 

Chronic pain's share of qualifying conditions fell to 31.9%, down from 64.5% in 2016. Posttraumatic stress disorder (PTSD) reached 28.6% and anxiety 16.7% by 2024. Conditions classified as having substantial or conclusive evidence of therapeutic benefit under the 2017 National Academies review fell to 38.3% of all reported conditions, down from 84.6% in 2016. 

Authorizing clinicians increased to almost 36,000 in 2024, up from less than 31,000 in 2020, but clinicians per 10,000 patients fell 13.4%. Caregivers numbered almost 110,000 in 2024. Caregiver rates ran highest in jurisdictions with recreational programs and in those allowing home cultivation. 

Researchers at the University of Michigan compiled registry data from publicly available reports, data requests, and communications with state medical cannabis programs. The registrations analysis covers 2016 to 2024; the clinician and caregiver analysis covers 2020 to 2024, with caregiver counts available for 2024 only. Qualifying conditions were categorized using the 2017 National Academies classifications. 

The 2017 National Academies review still anchors what counts as well-supported use, yet research has expanded since it was published, and the authors note the newer evidence is not reflected in their classifications. The bottleneck now is an updated evidence synthesis that catches the benchmark up to how patients actually use cannabis, with anxiety and PTSD at the front of the queue. 

"This widespread use also reflects the importance of continued rigorous clinical investigations of cannabis products in these conditions and more broadly to better understand possible risks and benefits," the authors conclude. 

Source: Boehnke KF, et al. (2026 Sep 29) Ann Intern Med. Trends in U.S. Medical Cannabis Registrations and Reasons for Use, 2016 to 2024 and U.S. Authorizing Clinicians and Medical Cannabis Caregivers: 2020–2024