Tourette’s syndrome (TS) is a condition that is characterized by vocal tics. It is a neuropsychiatric disorder, meaning that its mental characteristics are the result of underlying neuronal effects. TS is thought to be influenced by both environmental and genetic factors, and usually has an onset of childhood. Patients manifest a variety of symptoms which generally improve with age.
Research into the area of marijuana and TS has been led in large part by Dr. Kirsten Muller-Vahl and her research team. Muller-Vahl is a Professor of Psychiatry and an expert on TS, having published numerous papers not only about the effects of marijuana on TS, but about various aspects of TS itself.
In an early 1999 Letter to the Editor, Muller-Vahl and her colleagues reported on the success they had seen when treating a 25-year-old man with TS using tetrahydrocannabinol (THC). THC is the psychosomatic chemical found abundantly in marijuana. The man was able to find effective relief for both his motor and vocal tics.
In 2001, Muller-Vahl and colleagues set out to investigate whether treatment with THC could cause “cognitive impairment.” The study involved giving 12 patients doses of THC and testing their attention, memory, intelligence, reaction time, vigilance, and mood. Researchers concluded that, in patients suffering from TS, THC “did not cause cognitive impairment.”
Researchers didn’t wait long to begin another study in 2002 on the effects of THC in adults suffering with TS. They carried out a randomized, double-blind, placebo-controlled, crossover trial in which they administered THC to 12 patients. They confirmed all of their previous findings about THC as a safe compound that reduced both tics and other obsessive-compulsive tendencies. However, because only a single-dose trial was used, the authors called for a longer-term study to be done.
Many of the same authors answered their own call with a 2003 study which had the same setup as the one the year before, but which went on for 6 weeks. It was the first such long-term study of its kind. Much as the researchers expected, THC was once again shown to reduce the symptoms of TS. This led the authors to conclude that the body’s own endocannabinoid system plays a role in tic disorders.
In yet another 2003 study, Muller-Vahl and her team went back to expand their previous findings about the effect of THC on neuropsychological performance in patients suffering from TS. Over the course of 6 weeks, researchers discovered that not only were patient’s cognitive abilities not affected, but that their immediate verbal memory span actually tended to improve. They suggested that even longer studies should be done in this area.
The research into marijuana and TS quieted down for a while, but Muller-Vahl came back and published a review in 2013 which reiterated all of her previous findings and noted the need for more research into the area. She also stated that marijuana is often recommended by experts to their adult patients as a way to alleviate the symptoms of TS.