What Tourette’s syndrome is
Tourette’s syndrome is a neurological condition characterised by motor and vocal tics that begin in childhood. Tics are sudden, rapid, recurrent movements or sounds that are experienced as difficult to suppress. The condition frequently co-occurs with obsessive-compulsive features, attention deficit hyperactivity disorder, and anxiety. Standard treatment in the UK includes behavioural interventions such as habit reversal training and, where tics are disabling, medications such as alpha-2 agonists or antipsychotics. These medications carry significant side-effect burdens including sedation, weight gain, and metabolic changes, and many patients discontinue them.
Cannabis research on Tourette’s syndrome
Two randomised controlled trials of cannabinoid preparations for Tourette’s syndrome and chronic tic disorders have published results.
The CANNA-TICS trial, a 2023 multicentre Phase IIIb randomised double-blind placebo-controlled study, tested nabiximols (a THC/CBD oromucosal spray) against placebo in 97 adults with chronic tic disorders. The primary endpoint — a 25% or greater reduction in the Yale Global Tic Severity Scale total tic score after thirteen weeks — was met by 21.9% of the nabiximols group and 9.1% of the placebo group, but formal statistical superiority was not demonstrated. Secondary analyses showed trends toward improvement in tics, depression, and quality of life. An exploratory subgroup analysis suggested greater tic improvement in males, in patients with more severe tics, and in those with comorbid ADHD. A fitness-to-drive substudy of the same trial, published in 2024, found that nabiximols did not impair driving ability and was associated with an improvement from unfit to fit status in some patients who were unfit at baseline.
A separate 2023 randomised controlled crossover trial, reported in NEJM Evidence, tested an oral oil containing THC and CBD (5 mg/ml each) in people with severe Tourette’s syndrome. The primary outcome — the total tic score on the Yale Global Tic Severity Scale — decreased by a mean of 8.9 points during active treatment compared with 2.5 points during placebo, with a statistically significant treatment-by-visit interaction. The trial also reported that active treatment reduced tic-related impairment, anxiety, and obsessive-compulsive scores. However, cognitive side effects were common during the active-treatment period, with eight participants reporting slowed thinking, memory lapses, or poor concentration.
Human observational evidence adds context but not controlled confirmation. A 2023 Israeli retrospective study of 25 patients with Tourette’s syndrome using licensed medical cannabis for a mean of four years reported a subjective average tic reduction of 75%. The same study documented a statistically significant linear increase in monthly THC dose over time, averaging 0.6 to 0.7 grams per year, which the authors interpreted as suggesting tolerance. Most participants (88%) reported side effects, though medical cannabis was described as generally well tolerated.
A 2025 pilot randomised placebo-controlled crossover trial of medicinal cannabis in ten adolescents with Tourette’s syndrome found the study design feasible and acceptable to families. On the Clinical Global Impression-Improvement scale, three of seven participants who completed the crossover were rated as much improved on active treatment compared with one on placebo. Dizziness was the most common side effect, reported by 67% of participants. A related 2025 open-label study confirmed feasibility of medicinal cannabis administration in adolescents but did not add controlled efficacy data.
No human trials have tested isolated cannabinoids such as THC alone or CBD alone against placebo in Tourette’s syndrome. All published controlled studies have used combination preparations.
Compounds studied for Tourette’s syndrome
THC is the cannabinoid most studied in Tourette’s syndrome research. The CANNA-TICS trial tested nabiximols, which includes THC, and the NEJM Evidence crossover trial tested an oral THC/CBD oil. Both trials showed signal in tic reduction but neither trial isolated THC alone, so the contribution of THC specifically cannot be separated from the combination.
CBD was included in both published Tourette’s randomised controlled trials as part of THC/CBD combination preparations. No human trial has tested CBD alone for tics. The role of CBD in the observed effects is unknown.
Myrcene is a terpene with muscle-relaxant properties in animal models. Tics involve motor activity, but no human study has tested myrcene for tic reduction.
Linalool has anxiolytic properties in preclinical research. Anxiety and obsessive-compulsive features commonly co-occur with Tourette’s syndrome, and the NEJM Evidence trial found that the THC/CBD oil reduced anxiety and obsessive-compulsive scores. No human study has isolated linalool as a variable for Tourette’s outcomes.
Beta-caryophyllene activates CB2 receptors and has been associated with anti-inflammatory and anxiolytic effects in preclinical models. There is no human Tourette’s-specific research on beta-caryophyllene.
Limonene has been studied preclinically for mood effects. No human Tourette’s trial has tested limonene.
Limits of the evidence for Tourette’s syndrome
Two randomised controlled trials now provide controlled human data on cannabinoid preparations for tic disorders, making Tourette’s syndrome one of the better-studied conditions in this area. Neither trial established formal superiority of the cannabinoid preparation over placebo on its primary endpoint: the CANNA-TICS trial did not achieve statistical significance, and while the NEJM Evidence crossover trial reported a statistically significant tic reduction, the cognitive side-effect burden was notable.
Trial durations have been thirteen weeks at most. There are no randomised controlled data on the long-term safety or sustained efficacy of cannabinoid preparations in Tourette’s syndrome. The retrospective long-term data suggest subjective benefit but also document dose escalation consistent with tolerance — a concern for any long-term pharmacological approach to tic management.
The trials have been conducted by overlapping research groups. No independent replication from a different centre or country is currently available. The adolescent studies are pilot-scale only, with seven to ten completers each. No randomised controlled trial has tested a cannabinoid preparation against an active comparator such as an alpha-2 agonist or an antipsychotic.
The published trials used standardised pharmaceutical-grade cannabis extracts with defined THC/CBD ratios. The findings do not provide evidence about smoked cannabis, vaporised cannabis, high-THC products, or variable-ratio products obtained outside a clinical trial setting.
Sources
1. Muller-Vahl KR, et al. CANNA-TICS: Efficacy and safety of oral treatment with nabiximols in adults with chronic tic disorders — Results of a prospective, multicenter, randomized, double-blind, placebo controlled, phase IIIb superiority study. Psychiatry Research. 2023. PMID: 36878177. Study record DOI: 10.1016/j.psychres.2023.115135. 2. Mosley PE, et al. Tetrahydrocannabinol and Cannabidiol in Tourette Syndrome. NEJM Evidence. 2023. PMID: 38320199. Study record DOI: 10.1056/EVIDoa2300012. 3. Muller-Vahl KR, et al. The Effect of Nabiximols on Driving Ability in Adults with Chronic Tic Disorders: Results of a Substudy Analysis of the Double-Blind, Randomized, Placebo-Controlled CANNA-TICS Trial. Cannabis and Cannabinoid Research. 2024. PMID: 38265476. Study record 4. Anis S, et al. Licensed Medical Cannabis Use in Gilles de la Tourette Syndrome: A Retrospective Long-term Follow-Up. Cannabis and Cannabinoid Research. 2023. PMID: 37172308. Study record DOI: 10.1089/can.2022.0281. 5. A Pilot Randomized Placebo-Controlled Crossover Trial of Medicinal Cannabis in Adolescents with Tourette Syndrome. 2025. PMID: 40082070. Study record 6. Medicinal cannabis for tics in adolescents with Tourette syndrome. 2025. PMID: 40636988. Study record
