Dystonia is a neurological movement disorder characterized by abnormal muscle tension and involuntary, painful muscle contractions. It is the third most common movement disorder after Parkinson's disease and tremor, affecting more than 300,000 people in North America.
A small number of case reports and preclinical studies indicate that cannabinoids possess anti-dystonic activity.
A case study published in The Journal of Pain and Symptom Management reported improved symptoms of dystonia after inhaling cannabis in a 42-year-old chronic pain patient. Investigators reported that subject's subjective pain score fell from 9 to zero (on a zero-to-10 visual analog scale) following cannabis inhalation, and that the subject did not require any additional analgesic medication for the following 48 hours. "No other treatment intervention to date had resulted in such dramatic overall improvement in [the patient's] condition," investigators concluded.
A second case study appeared in the journal Movement Disorders reporting “significant clinical improvement” following cannabis inhalation in a single 25-year-old patient with generalized dystonia due to Wilson's disease.
A German research team at the Hannover Medical School reported successful treatment of musician's dystonia in a 38-year-old professional pianist following administration of 5 mg of THC in a placebo-controlled single-dose trial. Investigators reported “clear improvement of motor control” in the subject's affected hand, and noted, “[Two] hours after THC intake, the patient was able to play technically demanding literature, which had not been possible before treatment.” Prior to cannabinoid treatment, the subject had been unresponsive to standard medications and was no longer performing publicly. “The results provide evidence that … THC intake … significantly improves [symptoms of] … focal dystonia,” investigators concluded.
A 2002 randomized, placebo-controlled study investigating the use of the synthetic oral cannabinoid naboline (Cesamet) in 15 patients afflicted with generalized and segmental primary dystonia did not show a significant reduction in dystonic symptoms. By contrast, a case report finds that the daily administration of dronabinol was associated with decreased symptoms of paroxysmal dystonia.
A 2015 literature review opines that cannabis products likely possess a "promising role" for treating various movement disorders, including dystonia.
 Richter et al. 2002. Effects of pharmacological manipulations of cannabinoid receptors on severe dystonia in a genetic model of paroxysmal dyskinesia. European Journal of Pharmacology 454: 145-151.
 Chatterjee et al. 2002. A dramatic response to inhaled cannabis in a woman with central thalamic pain and dystonia. The Journal of Pain and Symptom Management 24: 4-6.
 Roca et al. 2004. Cannabis sativa and dystonia secondary to Wilson's disease. Movement Disorders 20: 113-115.
 Jabusch et al. 2004. Delta-9-tetrahydrocannabinol improves motor control in a patient with musician's dystonia (PDF). Movement Disorders 19: 990-991.
 Fox et al. 2002. Randomised, double-blind, placebo-controlled trial to assess the potential of cannabinoid receptor stimulation in the treatment of dystonia. Movement Disorders 17: 145-149.
 Deutsch et al. 2008. Current status of cannabis treatment in multiple sclerosis with an illustrative case presentation of a patient with MS, complex vocal tics, paroxysmal dystonia, and marijuana dependence treated with dronabinol. CNS Spectrums 13: 393-403.
 Barbara Koppel. 2015. Cannabis in the treatment of dystonia, dyskinesias, and tics. Neurotherapeutics 12: 788-792.