Medical Marijuana: The Evidence

The use of marijuana for medicinal purposes has a long history. Marijuana tea was prescribed in ancient China as early as 2700BC and the plant’s use for medicinal purposes spread throughout Asia, the Middle East and East Africa. Before its prohibition, cannabis extracts were sold in pharmacies in Europe and the United States. But what does the current scientific literature say about the medical use of marijuana? Is there evidence for the use of marijuana for any specific disease?

The Food and Drug Administration (FDA) and the Drug Enforcement Agency (DEA) have classified marijuana as a schedule I substance. Schedule I substances are considered to have no current accepted medical use and a high potential for abuse. This classification has consequences. Dr. Todd Handel, a Providence-based interventional physiatrist and doctor of physical medicine and rehabilitation who is board certified in pain medicine explained in an interview, “The way marijuana is scheduled by the FDA, as a class I substance, creates significant regulatory barriers and prevents a lot of research. There is anecdotal evidence, but not many large-scale, well-controlled clinical studies on the use of medical marijuana.”

The FDA has approved two drugs that contain a synthetic version of a substance contained in marijuana and one drug that contains a substance that mimics the action of a compound found in marijuana. These synthetic cannabinoid-based medicines are indicated for treating nausea and vomiting associated with chemotherapy and for appetite stimulation in wasting syndrome associated with HIV. The efficacy of cannabis products for treating these conditions is generally accepted at this point by the medical community. The FDA has not, however, approved marijuana itself as a safe and effective drug for any indication.

Despite the FDA classification, multiple reviews of medical literature suggest marijuana may be effective in treating other diseases. A clinical review from June 2015 published in the Journal of the American Medical Association reviewed 28 randomized clinical trials that investigated the effectiveness of marijuana in the treatment of chronic pain, neuropathic pain and spasticity due to multiple sclerosis. Several of the trials had positive results and suggest that marijuana and cannabinoids may have some benefit in treating these conditions. The College of Family Physicians of Canada published a review in August 2015 and it concluded, “There is evidence for the use of low-dose medical marijuana in refractory neuropathic pain in conjunction with traditional analgesics.” The studies reviewed, however, were limited by short duration as well as variable dosages and strengths of marijuana used. And as the review points out, “the long-term effects of psychoactive and neurocognitive effects of medical marijuana remain unknown.” The authors advise caution to doctors prescribing medical marijuana to patients.

There is also promising evidence for the use of cannabis in the treatment of certain types of seizures when unresponsive to traditional medication. The British Epilepsy Association, in a study published in February 2016, examined the experience of five pediatric epilepsy clinics in Israel treating children and adolescents with epilepsy unresponsive to traditional medication with CBD enriched cannabis oil. The oil had a CBD to THC ratio of 20:1, and 64% of patients had at least a 25% reduction in the frequency of seizures, causing the authors of the study to conclude that the results of the study were “highly promising.”

A number of major medical associations have weighed in on the potential of marijuana for medical use. In a position statement, the American Academy of Neurology (AAN) emphasizes their support for “rigorous research to evaluate the long-term safety and efficacy of medical marijuana and compounds derived from the plant.” The AAN also supports the reclassification of marijuana from Schedule I to Schedule II to allow for more medical research. They do not, however, advocate for the use of medical marijuana for neurological disorders at this time, citing the need for more research. The American Academy of Family Physicians’ position on medical marijuana advocates that usage be based on “high quality, patient-centered, evidence-based research and advocates for further studies into the use of medical marijuana and related compounds.” It also encourages the FDA to change marijuana’s classification to facilitate more research and to ensure funding for medical marijuana research.

Many doctors are now advocating for the use of medical marijuana when indicated. “The endo-cannabinoid system has the potential to improve health and alleviate suffering, and I advocate for its use in patients who are appropriate,” Dr. Handel stated. He did caution that there is still much we do not know about marijuana and echoed the call for more research. Dr. Handel also pointed out that, “There are many variables with medical marijuana consumption; the specific strain of marijuana, the CBD to THC ratio, the dosage and frequency of consumption, the method of consumption, and an individual’s response and side effects profile are all variables that can affect a patient’s response to marijuana. This highlights the need for doctors to be as knowledgable and up-to-date as possible on current medical literature regarding marijuana and the importance for patients to have an ongoing and honest relationship with their doctor in order to tailor treatment to be as effective as possible.”