Licensed Medical Cannabis Use in Gilles de la Tourette Syndrome: A Retrospective Long-term Follow-Up.

Background: Medical cannabis (MC) is widely used in clinical practice to treat Gilles de la Tourette syndrome (GTS). However, legislation, multiple modes of administration, and inconsistent plant preparations have limited trials to assess its benefits and long-term safety. For the past decade, licensed MC has been authorized in Israel for use in resistant GTS. We aimed to describe subjects' satisfaction, consumption habits, and THC dose increment during long-term usage. Materials and Methods: A retrospective longitudinal data collection (up to 9 years) on cannabis use habits and structured questionnaires evaluating disease characteristics and MC influence from GTS subjects being treated in the Movement Disorders Unit of the Tel-Aviv Medical Center, Israel. Results: Twenty-five patients (84% male) participated in the study. The mean duration of MC use was 4.0±2.3 years (range 0.5-10). The majority of patients (96%) consumed MC primarily, but not exclusively, through inhalation methods such as smoking or vaporizing dried inflorescence. A linear increase was observed in mean monthly THC dose (p<0.0001) with an average increase of 0.6-0.7 g/year. MC led to a subjectively reported reduction in tics (75% average reduction) and symptoms associated with common comorbidities of GTS. MC was generally well tolerated, although most participants (88%) reported experiencing side effects. Conclusions: A subset of GTS subjects who use MC long term under clinical observation may subjectively improve control of symptoms. Subject-led dose increase can indicate emerging tolerance. Large randomized controlled and observational long-term trials are required to confirm these observations.