Cannabis-Based Medicines May Ease Tics in Tourette Syndrome
A 2024 systematic review and meta-analysis found that cannabis-based medicines may reduce tic severity and premonitory urges in adults with Tourette syndrome, but the evidence is still too limited to establish cannabis as a routine treatment.
Published in the European Journal of Clinical Pharmacology, the review examined nine clinical trials and cohort studies involving 401 adults with Tourette syndrome. Only three studies, comprising 53 participants, provided data suitable for the researchers’ quantitative meta-analysis.
Tourette syndrome is a neurological condition involving persistent motor and vocal tics. Symptoms can fluctuate and may become more noticeable during periods of stress or excitement. Many people with Tourette syndrome also experience conditions such as attention-deficit/hyperactivity disorder, obsessive-compulsive disorder, anxiety, or depression. Treatment is generally aimed at reducing tics when they cause pain, injury, distress, or disruption to daily life.
What the review found
The studies examined several cannabis-based products, including preparations containing tetrahydrocannabinol (THC), nabiximols, dronabinol, and other cannabinoid formulations. Because the products, doses, study designs, and outcome measures varied, the findings cannot be treated as evidence for one standardized cannabis treatment.
Among the pooled results, participants showed a statistically significant reduction in total scores on the Yale Global Tic Severity Scale, a commonly used measure of tic severity. The analysis also found a significant reduction in scores on the Premonitory Urge for Tics Scale, which measures the uncomfortable sensations that can precede a tic.
However, the review found no statistically significant improvement in obsessive-compulsive symptoms measured with the Yale-Brown Obsessive Compulsive Scale. The authors also reported substantial variation among some of the studies, suggesting that the apparent benefits may not be consistent across patients or cannabis products.
Most importantly, the 401 participants included in the broader review should not be confused with the much smaller groups used for the pooled analyses. The strongest numerical findings were based on only a few dozen people, and several included studies were observational rather than randomized, placebo-controlled trials.
Why the findings are preliminary
The review’s results suggest a possible benefit, but they do not prove that cannabis caused the improvements. Uncontrolled studies can be influenced by placebo effects, changes in other medications, differences in dosing, or natural fluctuations in tic severity. Tourette symptoms can vary considerably over time, making well-designed control groups especially important.
The researchers called for larger, longer-term, placebo-controlled studies using standardized cannabinoid formulations and dosing schedules. Such trials would also need to assess cognitive, psychiatric, cardiovascular, and other potential adverse effects, as well as the risk of interactions with existing treatments.
Earlier controlled studies have offered some support for THC-containing medicines, but they have also been small. A randomized trial published in 2003 included only 24 patients, while a later crossover trial investigated an oral preparation containing both THC and cannabidiol. These studies provide useful signals for further research, but they are not large enough to establish cannabis as a broadly effective or safe treatment for Tourette syndrome.
How cannabis fits into current care
Behavioral treatment remains an important option. The U.S. Centers for Disease Control and Prevention describes comprehensive behavioral intervention for tics, or CBIT, as an evidence-based therapy that can help people recognize their tics, identify situations that worsen them, and practice competing responses.
Medication may also be considered when symptoms are severe or disruptive. Treatment decisions depend on a person’s age, symptoms, coexisting conditions, previous treatment response, and tolerance of side effects. The American Academy of Neurology’s practice guideline says there is limited evidence that THC or dronabinol may reduce tic severity in adults, while evidence for cannabidiol, nabiximols, nabilone, and different cannabis strains remains insufficient.
The guideline recommends particular caution with cannabis-based medicines. Short-term side effects may include dizziness, dry mouth, and fatigue, and cannabis can impair driving. The guideline advises avoiding these medicines in children and adolescents, during pregnancy or breastfeeding, and in people with psychosis. Where cannabis is used for treatment-resistant adult symptoms, it recommends medical supervision, the lowest effective dose, and regular reassessment.
For now, the 2024 review supports continued investigation rather than a change in standard care. Cannabis-based medicines may eventually prove useful for some adults with difficult-to-treat tics, but the available research does not yet show which products work best, who is most likely to benefit, or how their risks compare with established behavioral and pharmaceutical treatments.
