| Title | Research Limits on Knowledge of Benefit or Harm of Cannabis and Cannabinoids Use |
| Authors | Jamie Corroon, ND, MPH; Igor Grant, MD |
| Year | 2026 |
| Journal | JAMA |
Drs. Jamie Corroon and Igor Grant, Director of the CMCR, recently published a letter-to-the-editor in JAMA responding to a Systematic Review by Hsu and colleagues on the therapeutic use of cannabis and cannabinoids, arguing that the current evidence base should be interpreted with greater context and balance. While the Review concluded that evidence for most medical indications remains insufficient, the letter suggests this may risk overstating the weakness of the field without fully considering the barriers that have limited research.
A central argument is that cannabis’s longstanding federal classification has made rigorous clinical research difficult to conduct. According to the authors, this has restricted the kind of controlled trials typically expected to establish efficacy in medicine. In that sense, the limited evidence base may reflect regulatory obstacles as much as scientific uncertainty.
The letter also argues that discussions of risk should more clearly distinguish medical cannabis use from recreational use. The authors note that adults using cannabis for medical purposes, ideally under medical supervision, may differ substantially from those engaging in heavy recreational use. They caution that some adverse outcomes associated with recreational cannabis may be influenced by underlying neuropsychiatric or social factors, making direct comparisons problematic.
Drs. Corroon and Grant also take issue with how cardiovascular risks were presented in the Review. They note that although the Review cited potential cardiovascular harms, several large observational studies have not found associations between cannabis use and hypertension, myocardial infarction, or carotid atherosclerosis. Including those divergent findings, they argue, would better reflect the current state of evidence and avoid implying a stronger consensus than exists.
At the same time, the letter supports careful patient counseling. The authors agree that clinicians should discuss the limits of current evidence, possible adverse effects, and variability in product composition. Their broader point, however, is that reviews should aim for a balanced presentation of the literature, acknowledging not only gaps in evidence but also areas where harms remain unproven, inconsistent, or highly context-dependent.
View the pre-publication version submitted by the authors here. Note: This version is not the final published version.
Read the final published version here.
Citation: Corroon J, Grant I. Research Limits on Knowledge of Benefit or Harm of Cannabis and Cannabinoids Use. JAMA. Published online March 30, 2026. doi:10.1001/jama.2026.0770