Inclusion Criteria:  Males and females aged 12 - 18 years of age; DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) diagnosis of TS as assessed by the study clinician; TS severity defined as a score of 20 or higher on the Total Tic Severity section of the Yale Global Tic Severity Scale; No changes in either medication or other interventions in the 4 weeks prior to randomization, and intention to remain on same dose for the duration of the study; Participant and family have the ability to comply with the protocol requirements, in the opinion of the investigator; Agrees not to drive for the duration of the study.  Exclusion Criteria:  Non-English speaking parents; Participant history of psychosis, schizophrenia, bipolar disorder, or major depressive disorder, or a family history of psychosis; Taking anti-epileptic medications which interact with medicinal cannabis: clobazam, mTOR (mammalian target of rapamycin) inhibitors (e.g sirolimus, tacrolimus), anti-cancer agents, citalopram >20mg/day, escitalopram >10mg/day; Abnormal liver function tests defined as ALT (alanine transaminase) > twice ULN (upper limit of normal); Current use of illicit drugs or medicinal cannabis, or use in the 4 weeks prior to screening; Pregnant or intending to become pregnant during the study, or breastfeeding; History of clinically significant suicidal thoughts in the prior 12 months.