Neurologist evaluates evidence on the use of medical marijuana in brain diseases

July 07, 2014

By Andy Hyland

Gary Gronseth, M.D.

A review of the available research on the use of medical marijuana in brain diseases shows that certain forms of the drug can be helpful in treating some symptoms of multiple sclerosis, but do not appear to be helpful in treating drug-induced movements in Parkinson's disease.

Gary Gronseth, M.D., vice chairman of neurology at the University of Kansas Medical Center, helped conduct the evidence-based review for the American Academy of Neurology. The findings were presented in late April, 2014.

Gronseth says that in many cases, not enough evidence is available to show if medical marijuana was helpful. That was the case when examining whether medical marijuana was helpful in treating motor problems in Huntington's disease, tics in Tourette syndrome, cervical dystonia or seizures in epilepsy. In general, medical marijuana has been prescribed as a treatment for use only when standard treatment has not helped patients.

"We're not saying it doesn't work in these cases, just that we don't have enough good studies of the drug available in the literature to see whether it works or not," Gronseth says.

In cases where the drug was found to be helpful, it was taken in pill or oral spray form. The researchers did not find evidence to support that smoked medical marijuana could be effective for brain diseases.

"A big problem with studying smoked marijuana is that it's difficult to tell how much of the chemical THC that the patients are receiving," Gronseth says.

Gronseth, who has conducted similar exhaustive reviews of the available medical literature on various topics for the American Academy of Neurology, says that marijuana should be studied like any other drug.

Some safety concerns have been identified in studies so far. In at least two studies, patients reported side effects of nausea, increased weakness, behavioral or mood changes, suicidal thoughts or hallucinations, dizziness or fainting symptoms.

"The academy's review didn't necessarily suggest that the drug shouldn't be used," Gronseth says. "We just don't know a lot about how effective it is or a lot about how safe it is. We need more rigorous studies to help us find the answers to these questions."



Last modified: Jul 22, 2014