PHILADELPHIA—Certain forms of medical marijuana can help treat symptoms of multiple sclerosis (MS), but may not be helpful in treating levodopa-induced movements in Parkinson’s disease, researchers reported at the 66th Annual Meeting of the American Academy of Neurology (AAN). The researchers did not find enough evidence to show whether medical marijuana is helpful in treating motor problems in Huntington’s disease, tics in Tourette syndrome, cervical dystonia, and seizures in epilepsy. These conclusions are part of AAN’s review of scientific research on the use of medical marijuana in brain diseases. The findings were published in the April 29, 2014, print issue of Neurology.
“This review by the world’s largest association for neurologists is intended to help neurologists and their patients understand the current research on medical marijuana for the treatment of certain brain diseases,” said review author Barbara S. Koppel, MD, of New York Medical College in Valhalla, and Fellow of the AAN. “The AAN review also highlights the need for more high-quality studies of the long-term efficacy and safety of medical marijuana in the treatment of neurologic diseases.”
The AAN review concluded that only the pill or oral spray forms of medical marijuana can help treat symptoms of MS, including spasticity, certain types of pain (ie, pain related to spasticity, including painful spasms, and painful burning and numbness), and overactive bladder. Most of the MS studies examined pill or oral spray forms of medical marijuana. Two studies examined smoked medical marijuana for treating MS symptoms, but these studies did not provide enough information to show whether smoked medical marijuana is effective. “It’s important to note that medical marijuana can worsen thinking and memory problems, and this is a concern, since many people with MS suffer from these problems already due to the disease itself,” said Dr. Koppel.
In addition, the AAN review concluded that medical marijuana, in the form of synthetic tetrahydrocannabinol (THC) pills, likely does not help relieve abnormal movements that can develop in the late stages of Parkinson’s disease as a result of levodopa.
Medical marijuana use does entail safety concerns. In at least two studies, participants reported side effects such as nausea, increased weakness, behavioral or mood changes, suicidal thoughts or hallucinations, dizziness or fainting symptoms, fatigue, and feelings of intoxication. There were reports of two seizures. Mood changes and suicidal thoughts are of special concern for people with neurologic illness, who are at an increased risk for depression and suicide. The risk of serious psychologic effects is approximately 1%, according to the studies.
The only two medical marijuana pills with FDA approval contain THC. “The psychoactive side effects, like feeling intoxicated, seemed to come from the THC,” said Dr. Koppel. “They’re trying to create pills that are leaning more toward the cannabinoid, which has the therapeutic effects with fewer psychoactive side effects.”
Clinicians who practice in states where medical marijuana is legal may recommend the drug for the MS symptoms that respond to it, Dr. Koppel added. “The problem is that the studies are done very rigorously with a certain amount of THC versus cannabinoid. The type of marijuana you can buy so far is not so rigorously defined.” Clinicians also should warn their patients about marijuana’s potential side effects.
In general, medical marijuana is prescribed as a treatment only when standard treatment has not helped. In most of the studies reviewed, patients were allowed to continue their standard treatments. The AAN review is endorsed by the American Autonomic Society, the American Epilepsy Society, and the International Rett Syndrome Foundation.
—Erik Greb