Cannabis-based medicine in treatment of patients with Gilles de la Tourette syndrome

Introduction: Gilles de la Tourette syndrome (GTS) is a childhood onset disorder characterised by the presence of motor and vocal tics. The guidelines of both the American Academy of Neurology (AAN) as well as the European Society for the Study of Tourette Syndrome (ESSTS) recommend behavioural therapy and pharmacotherapy, mainly with antipsychotics, as first line treatments for tics. In spite of these well-established therapeutic approaches, a significant number of patients are dissatisfied because of insufficient tic reduction or intolerable side effects. Previous studies have suggested that cannabis-based medicine (CBM) might be an alternative treatment in these patients.

Material and methods: Two reviewers (KS, NS) searched the electronic database of PubMed on 1 July, 2021 for relevant studies using the search terms: (‘Tourette syndrome’ [MeSH Terms] OR ‘Gilles de la Tourette syndrome’ [MeSH Terms] OR ‘tic disorders’ [MeSH Terms] OR ‘tics’ [MeSH Terms] OR ‘tic disorders’[Title/Abstract]) AND (‘cannabis-based medicine’ [Title/Abstract] OR ‘cannabis’ [Title/Abstract] OR ‘dronabinol’ [Title/Abstract] OR ‘nabiximols’ [Title/Abstract] OR ‘tetrahydrocannabinol’ [Title/Abstract] OR ‘THC’ [Title/Abstract] OR ‘cannabidiol’ [Title/Abstract], limit: ‘humans’. These studies were further reviewed for additional relevant citations. The titles and abstracts of the studies obtained through this search were examined by two reviewers (KS, NS) in order to determine article inclusion. Discrepancies were addressed by the reviewers through discussion and eventually conversation with the senior reviewer (KMV).

Results: Although the amount of evidence supporting the use of CBM in GTS is growing, the majority of studies are still limited to case reports, case series, and open uncontrolled studies. To date, only two small randomised controlled trials (RCTs) using tetrahydrocannabinol (THC, dronabinol) have been published demonstrating the safety and efficacy of this intervention in the treatment of tics in patients with GTS. On the other hand, another RCT with Lu AG06466 (formerly known as ABX-1431), a modulator of endocannabinoid neurotransmission, has failed to prove effective in the therapy of GTS. Accordingly, under the guidelines of both the ESSTS and the AAN, treatment with CBM is categorised as an experimental intervention that should be applied to patients who are otherwise treatment-resistant.

Conclusions: Increasing evidence suggests that CBM is efficacious in the treatment of tics and psychiatric comorbidities in patients with GTS. The results of ongoing larger RCTs, such as CANNA-TICS (ClinicalTrials.gov Identifier: NCT03087201), will further clarify the role of CBM in the treatment of patients with GTS.