Preliminary evaluation of the efficacy, safety, and costs associated with the treatment of chronic pain with medical cannabis.

Introduction: Medical cannabis (MC) is commonly claimed to be an effective treatment for chronic or refractory pain. With interest in MC in the United States growing, as evidenced by the 29 states and 3 US districts that now have public MC programs, the need for clinical evidence supporting this claim has never been greater.

Methods: This was a retrospective, mirror-image study that investigated MC's effectiveness in patients suffering from chronic pain associated with qualifying conditions for MC in New York State.