• Involuntary movements (chorea): Limited and mixed. A 2009 crossover trial of prescription nabilone in 44 patients suggested improvement in movement and behavior, while a 2016 trial of a THC/CBD mouth spray in 24 patients found it safe but no better than placebo (summary of trials).
• Dystonia and irritability: Limited. In a 2018 series of 7 patients with early-onset disease, cannabinoids eased dystonia and irritability (Saft 2018).
• Slowing the disease: Not established; only animal studies.

Compared with standard treatment: FDA-approved medicines for chorea (tetrabenazine, deutetrabenazine, valbenazine) have stronger evidence.

Good to know: THC can worsen balance and thinking, and falls are already a risk. One report found nabilone increased chorea in a patient. Start very low with a caregiver involved.

What to ask for: Low-dose oral THC, ideally prescription nabilone or dronabinol, prescribed with the neurologist.