St. Paul, Minn. – Anecdotal claims of the benefits of marijuana for people with multiple sclerosis (MS) have been around for years, but the few studies on the topic have been small and inconclusive. A new study suggests that marijuana derivatives do not improve MS symptoms, but researchers say more studies need to be done before conclusions can be reached.
At 16 patients, the study is the largest randomized, controlled clinical trial on this topic. The study is published in the May 14 issue of Neurology, the scientific journal of the American Academy of Neurology.
The patients were given capsules of a placebo, marijuana plant-extract, or synthetic tetrahydrocannabinol (THC), which is the active ingredient in marijuana, for four weeks each.
The patients had severe spasticity, the MS symptom that some reports have found the most responsive to marijuana treatment. Spasticity, one of the more common symptoms of MS, involves involuntary muscle stiffness and/or spasms.
The study found that both the synthetic THC and the plant-extract were safe for patients, although side effects such as dizziness and headache were more common with plant-extract treatment.
The study was designed to determine whether the marijuana derivatives are safe for patients. It was not designed to determine how effective they are in treating MS symptoms.
"Due to the limited numbers of patients, we can''''t draw any definite conclusions," said study author Joep Killestein, MD, of the VU Medical Center in Amsterdam, Netherlands. "But these results suggest that synthetic THC and plant-extract do not improve symptoms for MS patients."
There were no differences in the patients'''' level of spasticity while taking placebo and either of the marijuana derivatives, according to neurologist Chris H. Polman, who supervised the study. Patients'''' muscle tone improved while on the drug treatments, but their ratings on a scale measuring overall disability declined. In their own rating of their symptoms, patients said they did worse while using the drugs than when on the placebo.
The researchers noted a couple possible reasons why no benefit was found from using the marijuana derivatives.
"One could be the way the drug was given - in a capsule," Killestein said. "THC is reasonably absorbed by the stomach, but the process is slow and it is absorbed faster in some people than in others."
Another possible explanation is that the dose used was too low to show a benefit, Killestein said. "But with the number of side effects patients experienced, especially with the plant-extract, we wouldn''''t recommend using a higher dosage," he said.
The study was financially supported by the Dutch Ministry of Health, Welfare and Sport.
In an editorial accompanying the article, neurologist Alan J. Thompson, MD, of Institute of Neurology at University College London in England, noted that a study of 660 patients receiving plant-extract, THC and placebo is underway in the United Kingdom.
"Right now, fundamental questions about the potential value of cannabis (marijuana) remain unanswered," Thompson said. "Hopefully they will be adequately addressed in the U.K. study."
The American Academy of Neurology, an association of more than 19,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as stroke, Alzheimer's disease, epilepsy, Parkinson's disease, autism and multiple sclerosis.
For more information about the American Academy of Neurology, visit www.aan.com.
- end -