July 1, 2015
Study Finds Strong Evidence Lacking for Medical
Marijuana Effectiveness

Bristol, England—With about half of the states in the U.S. legalizing medical marijuana in some form, a surprising lack of evidence continues to exist for the effectiveness of cannabinoids for a variety of conditions, while adverse effects (AEs) are under-recognized, according to a new study.

The report, which appears in a recent issue of the Journal of the American Medical Association (JAMA), was based on an analysis of the findings of nearly 80 randomized trials that included about 6,500 participants.

A study team led by researchers from the University of Bristol in England found moderate-quality evidence to support the use of cannabinoids for the treatment of chronic pain, with 37% on cannabinoids versus 31% not using them demonstrating a reduction in pain. Lower-quality evidence associated the compounds with improvement in nausea and vomiting due to chemotherapy, sleep disorders, and Tourette syndrome—47% in the intervention groups versus 20% in patients not using cannabinoids.

Background information in the article points out that 23 states and the District of Columbia have laws to permit the medical use of cannabis in some circumstances, as do many other countries.

Through the meta-analysis, the researchers found that, while most studies suggested that cannabinoids were associated with improvements in symptoms, those associations did not always reach statistical significance. For example, there was low-quality evidence for having no effect on psychosis and very low-quality evidence linking medical marijuana to improvement in anxiety or depression.

At the same time, cannabinoids increased risks of short-term—sometimes serious—AEs, including dizziness, dry mouth, nausea, fatigue, somnolence, euphoria, vomiting, disorientation, drowsiness, confusion, loss of balance, and hallucination. The type of cannabinoids or how they were administered did not appear to make a difference in their effect, whether beneficial or harmful. In addition, only two studies evaluated cannabis without finding evidence that it differed from other cannabinoids.

“Further large, robust, randomized clinical trials are needed to confirm the effects of cannabinoids, particularly on weight gain in patients with HIV/AIDS, depression, sleep disorders, anxiety disorders, psychosis, glaucoma, and Tourette syndrome are required,” study authors conclude. “Further studies evaluating cannabis itself are also required because there is very little evidence on the effects and AEs of cannabis.”

Deepak Cyril D'Souza, MD, and Mohini Ranganathan, MD, of Yale University School of Medicine in New Haven, Connecticut, suggest in an accompanying editorial that states which have approved medical marijuana may have acted too quickly without enough evidence basis.

“If the states’ initiative to legalize medical marijuana is merely a veiled step toward allowing access to recreational marijuana, then the medical community should be left out of the process, and instead marijuana should be decriminalized,” D’Souza and Ranganathan write.

“Conversely, if the goal is to make marijuana available for medical purposes, then it is unclear why the approval process should be different from that used for other medications,” they add. “Evidence justifying marijuana use for various medical conditions will require the conduct of adequately powered, double-blind, randomized, placebo/active controlled clinical trials to test its short- and long-term efficacy and safety.”

“The federal government and states should support medical marijuana research,” according to the commentators. “Since medical marijuana is not a life-saving intervention, it may be prudent to wait before widely adopting its use until high-quality evidence is available to guide the development of a rational approval process.”
U.S. Pharmacist Social Connect