Scientists are investigating whether cannabis can reduce the symptoms associated with Tourette syndrome. The preliminary evidence suggests that the drug could help those with the neuropsychiatric disorder by reducing involuntary tics.

A new study published May 3, 2017, in The Journal of Neuropsychiatry and Clinical Neurosciences has found that Tourette syndrome patients find cannabis to be both effective and well tolerated.

“This topic was brought to our attention by patients,” explained the study’s corresponding author, Elia Abi-Jaoude of the University of Toronto. “Several of my patients with Tourette syndrome had noticed that if they used some marijuana, their tics decreased significantly. We began prescribing medical cannabis at our clinic and were struck by the improvements we saw in tics and related symptoms. We eventually decided that we should investigate this topic further.”

The study was based on 19 patients who had been using cannabis to treat moderate to severe symptoms of Tourette syndrome at the Toronto Western Hospital. All of the patients had been using cannabis regularly for at least 2 years.

They all reported clinically significant symptom relief, and all except one said they had experienced a decrease in tic severity.

“The majority of patients for whom we prescribed cannabis had a significant improvement in their tics and related symptoms,” Abi-Jaoude told PsyPost. “While the cannabis was generally well tolerated, most patients experienced side effects, such as sleepiness, decreased concentration, and anxiety.”

But Abi-Jaoude cautioned that the research has a number of important caveats.

“This was a retrospective study, so there may be a ‘recall bias’ when people try to compare how they are doing now to how they were doing before starting cannabis,” he explained. “Moreover, this was an observational study that did not have a placebo control; thus, we cannot know to what extent the improvements we saw can be accounted for by a placebo effect.

“Also, since this was a relatively small study, uncommon but serious side effects may not have been picked up. In addition, since there was much variability in the cannabis strains that were used by our study patients, we were not able to make reliable conclusions about which cannabis strains or ingredients are most helpful for tics and related symptoms.”

Though the initial findings are encouraging, there still needs to be more research to confirm that cannabis is an effective treatment.

“I believe that cannabis is a promising treatment for tics and related symptoms,” Abi-Jaoude said. “However, unlike what may be suggested by headlines, it is not a panacea. Also, like any other medication we prescribe, it is not without risks. As a next step, we are planning to carry out a controlled, double-blind trial with different cannabis strains for tic symptoms. We hope that with further research we can get a clearer picture of the potential benefits and risks with using cannabis for tics and related symptoms.”

The study, “Preliminary Evidence on Cannabis Effectiveness and Tolerability for Adults With Tourette Syndrome“, was also co-authored by Lei Chen, Patrina Cheung, Tracy Bhikram, and Paul Sandor.