Challenges for Clinical Cannabis and Cannabinoid Research in the United States.

Significant changes have occurred in the policy landscape surrounding cannabis legalization, production, and use around the globe and across the United States. With widespread availability of novel cannabis and cannabis-based products, there is an urgent need to understand their safety and effectiveness for medical indications. Three primary barriers contribute to the difficulty in initiating research geared toward answering the most pressing public health questions: the US regulatory status of cannabis and cannabinoids, sources for cannabis and cannabinoid study medications, and limited funding and resources to support studies. Despite these hurdles, research is rapidly increasing, and recent changes in the United States have paved the way for exciting new work. Here, challenges and barriers to cannabis and cannabinoid research are described from the perspectives of the National Institute on Drug Abuse, National Institutes of Health; the US Food and Drug Administration; and 2 clinical researchers. Barriers specifically to studying cannabis, cannabinoids, and cancer are emphasized.