U.S. Policy Responses to Calls for the Medical Use of Cannabis.

This paper discusses the evolution of U.S. policy responses to calls to allow patients to use cannabis for medical purposes. It first summarizes the research evidence on the safety and efficacy of cannabinoids for various medical uses. It then outlines the challenges in developing new pharmaceutical cannabinoids that are safe, effective, and acceptable to patients. It briefly describes the strengths and limitations of the different ways in which U.S. states have allowed patients to use cannabis for medical purposes. These include allowing access for research trials only, allowing medical necessity as a defense against prosecution, and allowing commercial medical dispensaries to provide cannabis to approved patients. It argues that liberal definitions of indications for medical cannabis use and the commercialization of medical cannabis supply in California have produced the de facto legalization of recreational cannabis use.