(TS), results of a double-blind, placebo-controlled, crossover study show.
“In a methodologically robust manner (and independent of any drug company sponsorship), we provide evidence for the effectiveness of repeated dosing with THC:CBD vs. placebo in tic suppression, as well as reduction of comorbid anxiety and obsessive-compulsive disorder in severe TS,” neuropsychiatrist and lead investigator Philip Mosley, PhD, said in an interview.
The results offer support to people with TS who “want to approach their doctor to try medicinal cannabis when other drugs have not worked or are intolerable,” said Dr. Mosley, of the Wesley Research Institute and QIMR Berghofer Medical Research Institute, Herston, Australia.
The study was published online in NEJM Evidence.
A viable treatment option
Twenty-two adults (mean age, 31 years) with severe TS received THC:CBD oil titrated upward over 6 weeks to a daily dose of 20 mg of THC and 20 mg of CBD, followed by a 6-week course of placebo (or vice versa). Six participants had not previously used cannabis.
The primary outcome was the total tic score on the Yale Global Tic Severity Scale (YGTSS; range 0 to 50 with higher scores = greater tic severity).
The mean baseline YGTSS total tic score was 35.7. At 6 weeks, the reduction in total tic score was 8.9 with THC:CBD vs. 2.5 with placebo.
A linear mixed-effects model (intention-to-treat) showed a significant interaction of treatment and visit number (P = .008), indicating a greater decrease (improvement) in tic score over time with THC:CBD, the study team reported.
On average, the magnitude of the tic reduction was “moderate” and comparable to the effect observed with existing treatments such as antipsychotic agents, the investigators noted.
THC:CBD also led to a reduction in other symptoms associated with TS, particularly symptoms of OCD and anxiety.
The symptomatic response to THC:CBD correlated with serum metabolites of the cannabinoids, further supporting a biological relationship, the researchers noted.
There were no serious adverse events. Adverse effects with THC:CBD were generally mild. The most common adverse effect was cognitive difficulties, including slowed mentation, memory lapses, and poor concentration.
“Like many studies of psychoactive compounds, blinding among participants was a problem,” the researchers noted. Despite best efforts to conceal treatment allocation and match placebo to the active agent in terms of color and smell, most participants were able to correctly guess their treatment order.
Based on the findings in this small trial, larger and longer trials of THC:CBD in TS are warranted, they concluded.
“We need a plurality of treatment options in Tourette syndrome. For some, antipsychotics are effective tic-suppressing agents but for many these benefits are complicated by side effects such as weight gain & sedation,” Dr. Mosley tweeted. “Cannabinoids are a biologically plausible therapeutic agent. The body’s own ‘endocannabinoid’ receptors are concentrated in the basal ganglia – the neuroanatomical nexus of TS.”
The study was funded by the Wesley Medical Research Institute, Brisbane, and the Lambert Initiative for Cannabinoid Therapeutics, a philanthropically funded research organization at the University of Sydney, Australia. Dr. Mosley reports no relevant financial relationships.
A version of this article first appeared on Medscape.com.