THC Significantly Reduced Tics in Two Controlled Trials for Tourette Syndrome | Research

The takeaway

Two controlled trials found THC significantly reduced tics in Tourette syndrome without causing significant adverse effects, and experts recommend THC for treatment-resistant adults despite calls for larger trials.

Read this if you or someone you know has Tourette syndrome that has not responded to standard treatments.

Both controlled trials showed significant tic reduction with THC vs. placebo

What the researchers found

The review examined the evidence for cannabinoid treatment of Tourette syndrome (TS). Two controlled trials investigated THC for TS and both found significant tic reduction compared to placebo on both self-rating and examiner-rating scales, without significant adverse effects.

The available data on THC's effect on obsessive-compulsive symptoms (which commonly co-occur with TS) were inconsistent. A Cochrane review concluded that definitive conclusions could not be drawn due to the lack of larger, longer trials. Despite this formal appraisal, many experts recommend THC for treatment-resistant adult TS patients, reflecting a gap between the formal evidence bar and clinical judgment.

Why it matters

Tourette syndrome can be severely debilitating, and existing treatments have significant side effects. The consistent finding of tic reduction across two controlled trials, combined with a good safety profile, positions THC as a viable option for treatment-resistant patients.

The numbers in context

2 controlled trials of THC for TS. Both showed significant tic reduction vs. placebo. Self-rating and examiner-rating scales both improved. No significant adverse effects. Expert recommendation for treatment-resistant adults.

How the study worked

Narrative review covering anecdotal reports, two controlled trials, and expert recommendations for cannabinoid use in Tourette syndrome. Also discussed the broader context of approved cannabinoid medications.

What this study cannot tell us

Only two controlled trials exist, both small. The Cochrane review found the evidence insufficient for definitive conclusions. Long-term safety data are lacking. The trials were conducted by similar research groups. Optimal dosing, formulation, and treatment duration remain unclear.

How to read the evidence

Two small controlled trials with consistent results; moderate evidence supported by expert consensus.

When this study was published

Published in 2013. Interest in cannabinoids for Tourette syndrome has continued, with some additional trials underway.

The bigger picture

TS is a condition where cannabinoid treatment has unusually strong expert endorsement relative to the formal evidence base. The two controlled trials, while small, produced consistent results that align with decades of anecdotal reports, creating a convergence of evidence that has shifted clinical practice.

Questions still open

Would larger trials confirm the tic-reducing effect? Is THC superior to CBD for TS? What is the optimal dosing regimen? Would pharmaceutical cannabinoid preparations be better than whole-plant cannabis for TS?

Common questions

Does cannabis help Tourette syndrome?

Two controlled trials found that THC significantly reduced tics in Tourette syndrome compared to placebo, and this aligns with anecdotal reports going back decades. The evidence is considered sufficient by many experts to recommend THC for adults who have not responded to standard treatments, though larger trials are still needed for definitive conclusions.

Is THC safe for Tourette syndrome patients?

The two controlled trials reported no significant adverse effects from THC treatment. However, long-term safety data are limited. THC can cause cognitive effects, psychomotor impairment, and has abuse potential. For TS specifically, the risk-benefit calculation may favor THC when other treatments have failed, but this should be evaluated on an individual basis.

Read the original research

Treatment of Tourette syndrome with cannabinoids.

Behavioural neurology, 27(1), 119-24

View on PubMed ↗Publisher’s paper ↗

Citation

Müller-Vahl, Kirsten R. (2013). Treatment of Tourette syndrome with cannabinoids.. Behavioural neurology, 27(1), 119-24. https://doi.org/10.3233/BEN-120276