What does the research say?
In the conditions on this page, there are nine studies in which participants were assigned to groups at random and compared with a dummy treatment (placebo); a total of 153 people took part, and the largest had 44 people. Two were done in essential tremor, two in dystonia, two in eyelid spasm and three in Huntington’s disease. Most had a crossover design: the same person used the active product for one period and the placebo for another, without knowing which one they were taking. The researchers themselves also write that the studies were small and that the results should be considered preliminary findings.
In essential tremor, in a study with 19 patients in Brazil, participants took 300 mg of pure CBD once and a placebo once, two weeks apart. Within three and a half hours after the dose, no clear difference was seen between CBD and placebo in the arm tremor score, in tasks such as writing and drawing, or in the doctor's overall impression; the researchers note that this study cannot tell us the effect of regular use. In a pilot study with seven men in the US, a product containing 5 mg of THC and 100 mg of CBD in each capsule was used for two weeks, up to at most three capsules a day; tremor measured by spiral drawing on a tablet and the clinical tremor score did not change clearly compared with the placebo period. Tremor decreased to a similar extent from baseline in both periods, by about half; the researchers attribute this to first-visit nervousness wearing off and to getting used to the test. This also shows why observations without a placebo period can be misleading.
The oldest data in dystonia are from 1986: five patients were given pure CBD for six weeks, increasing from 100 mg to 600 mg a day, and there was no comparison group. An improvement of 20% to 50% in dystonia was reported; however, in two patients who also had signs of Parkinson’s, slowness of movement and resting tremor increased at doses above 300 mg a day. Two controlled studies tested THC or THC-like medicines: in the UK, nabilone (a synthetic THC-like medicine) given once to 15 patients did not reduce the dystonia score clearly more than placebo; in a study with nine women with cervical dystonia, synthetic THC (dronabinol) used for a few weeks also made no difference. The journal of this last study is not in PubMed; its results were taken from what two systematic reviews report.
There are two small controlled studies in eyelid spasm; both were done in patients who had not improved enough with botulinum toxin (Botox) injections (in the US study, participants continued their injections; the abstract of the Israeli study does not include this information). In the US, in a study with 12 people whose symptoms persisted despite botulinum toxin, everyone used pure CBD (200 mg a day, under the tongue) and placebo for three months each. In video-based measurement, during the CBD period, the median duration of eyelid closures fell by about 16% from baseline (by about 5% in the placebo period), and on this measure the difference from placebo was clear; however, this was the only measure that differed from placebo: no clear CBD-specific difference was seen in the number, speed or amplitude of closures, and the small improvement on the symptom scale used by doctors was not statistically significant either. In Israel, in a study with six patients who had not improved enough with botulinum toxin (three on cannabis oil, three on placebo), according to a review, spasm attacks were much shorter in the first six weeks in the group taking a THC-dominant (3.2% THC, 0.1% CBD) under-the-tongue oil than in the placebo group. However, there were only three people in each group; the difference between the groups persisted in the following six weeks, when both groups were using the oil, and baseline values were not reported. So it is not possible to know how much of the difference came from the oil; the details of the study could not be read either.
Systematic reviews that pool the studies found no evidence of benefit from cannabinoids in dystonia: in a 2022 meta-analysis, none of the three small studies in dystonia (one done in people with Huntington’s disease) showed a significant difference; a 2022 review collecting the controlled studies in movement disorders also found no improvement in the two dystonia studies. No systematic review specific to essential tremor or eyelid spasm was found. Real-world data look more positive, but there is no comparison group: in Israel, 23 patients with dystonia using licensed medical cannabis reported an average improvement of 47%; those with generalized dystonia and those who smoked cannabis described more improvement, and the reported improvement was linked to the THC proportion of the product. In 25 children with complex movement disorders, improvement in dystonia and muscle stiffness was reported over five months with two CBD-rich oils that also contained a small amount of THC, but there was no placebo group. Studies like these cannot separate out the placebo effect and expectations.
Three small controlled studies with cannabinoids were done in Huntington’s disease, and all three had a crossover design. In the study published in 1991, 15 patients who were not taking neuroleptic medicines were given pure CBD at 10 mg per kilogram of body weight a day, on average about 700 mg a day, for six weeks; no clear difference from placebo was seen in involuntary movements, other measures or side effects. In a study with 26 patients in Spain, a mouth spray containing THC and CBD was used for 12 weeks; the main aim of the study was to test safety, and there was no difference from placebo in movement, thinking, behavior and daily functioning scores. In a study with 44 patients, nabilone, a synthetic THC-like medicine, did not affect the overall movement score, the main measure, differently from placebo; a small improvement in involuntary movements (chorea) and on a psychiatric symptoms scale was reported, and the researchers consider this a preliminary finding that needs to be tested in a larger and longer study. In a single case report, however, nabilone increased involuntary movements. In a case series of seven patients, an improvement in the dystonia score was reported after cannabinoid treatment was started; but there was no comparison group and the authors present patients who showed clear improvement, so it is not possible to know how much of the improvement came from the treatment. Reviews and guidelines interpret these small studies differently: a 2024 systematic review considers nabilone and the spray containing THC and CBD 'possibly ineffective' at reducing involuntary movements, while the German Society of Neurology's 2023 guideline mentions THC and nabilone as 'possibly helpful' for movement symptoms, although the same guideline also writes that no effect on symptoms was seen in the 12-week spray study; according to a 2025 review, the nabilone study is the only controlled study with a positive result for psychiatric symptoms. In Huntington’s, the strength of evidence is very weak both for CBD and for THC-containing products.
Parkinson’s disease, Tourette syndrome and MS are covered on separate pages of the site; studies on tremor and movement symptoms caused by these diseases were not included in this page's table.
Strength of evidence: ●○○○ Very weak evidence. Finding: Not studied enough. What does this mean?
Ongoing research on this topic
No ongoing CBD trial on this topic appears on ClinicalTrials.gov right now. All ongoing trials
Possible side effects and drug interactions
No significant side effects were seen in short studies with pure CBD: in the eyelid spasm study, all 12 people completed the study, and only one had softer stools. In people with Huntington’s disease, with an average of about 700 mg of pure CBD a day for six weeks, no difference from placebo was seen on a cannabis-specific side effect scale or in laboratory tests. In the 1986 dystonia study, however, at doses increased up to 600 mg a day, low blood pressure, dry mouth, slowed movements, light-headedness and sleepiness were seen; in two patients who also had signs of Parkinson’s, slowness of movement and resting tremor increased.
Side effects were more common with THC-containing products. In the essential tremor study, all seven people reported reduced attention during the THC and CBD capsule period; dizziness, sleepiness, unsteadiness and forgetfulness were also more common than in the placebo period, and one participant briefly fainted after taking the product on an empty stomach. In the nabilone study in dystonia, two patients left the study because of a drop in blood pressure on standing and marked sleepiness. In Huntington’s disease, no serious side effects or worsening of symptoms were seen over 12 weeks with the mouth spray containing THC and CBD; according to a review, the most common side effects were dizziness and impaired attention. In the 44-person nabilone study in Huntington’s, no psychotic episodes were seen and the medicine was generally well tolerated; however, according to a review, there were three serious side effects and two people left the study because of them, and the most common side effects were sleepiness and forgetfulness. In a single case report, nabilone also increased involuntary movements. In patients with dystonia using medical cannabis, dry mouth, sleepiness and dizziness were reported most often; six of 23 people had psychiatric side effects such as anxiety or worsening mood, and these mostly improved after switching to a product with less THC.
These studies did not look at drug interactions separately. CBD can slow the breakdown of some medicines in the body; this matters for people who take medicines regularly for tremor, dystonia or Huntington’s disease.
To check interactions with the medicines you take: CBD drug interaction checker.
How was CBD used in studies?
The doses used in the studies varied greatly by product and condition. Pure CBD was given as a single 300 mg dose in essential tremor (study dose; not a personal recommendation), as 100 mg twice a day under the tongue as an add-on to botulinum toxin (Botox) in eyelid spasm (study dose; not a personal recommendation), and in the 1986 dystonia study increasing from 100 mg to 600 mg a day over six weeks (study dose; not a personal recommendation). In Huntington’s disease, pure CBD was used for six weeks at 10 mg per kilogram of body weight a day, that is, on average about 700 mg a day (study dose; not a personal recommendation).
Among THC-containing products, the capsule in the essential tremor study contained 5 mg of THC and 100 mg of CBD; it was started at one capsule a day and increased as tolerated to at most three capsules, that is, at most 15 mg of THC and 300 mg of CBD a day (study dose; not a personal recommendation). In the cervical dystonia study, synthetic THC was increased gradually with 2.5 mg tablets up to at most 15 mg a day; in dystonia, nabilone was given once at 0.03 mg per kilogram of body weight; in eyelid spasm, the THC-containing oil drops were increased individually, and in the final weeks an average of five to six drops a day were used (study doses; not a personal recommendation). In Huntington’s disease, the mouth spray containing THC and CBD was used for 12 weeks at up to 12 sprays a day (at most about 32 mg of THC and 30 mg of CBD), and nabilone at 1 or 2 mg a day (study doses; not a personal recommendation).
In these studies, the dose was adjusted according to the research plan and under a doctor's supervision; most lasted a few weeks or a few months. There are no controlled studies of long-term use.
Study details (for health professionals)
There are nine randomized controlled trials with cannabinoids in essential tremor, dystonia, blepharospasm and Huntington’s disease (153 randomized participants in total, 6–44 per study). In essential tremor, a single 300 mg dose of pure CBD (19 people, crossover) did not change tremor scores; a THC and CBD capsule (at most 15 mg THC + 300 mg CBD/day, 2 weeks; 7 randomized, 5 completed) did not differ from placebo on the primary outcome, tremor amplitude by spiral drawing, or on the clinical scale, and one participant had a convulsive syncope that may have been drug-related. In dystonia, single-dose nabilone (15 people) and dronabinol in cervical dystonia (at most 15 mg/day, 9 people) did not differ from placebo; the dronabinol study is in a journal not indexed in PubMed, and its figures come from two systematic reviews. In blepharospasm, 200 mg/day of pure CBD added to botulinum toxin (12 people, crossover with 3-month periods) shortened video-measured closure duration clearly more than placebo (−15.8%; p < 0.001 between CBD and placebo; the only measure that remained different from placebo after correction for multiple comparisons), the CBD–placebo difference in closure amplitude was not significant (p = 0.08), closure velocity changed similarly in both periods (p = 0.93), and the difference on the clinical scale was not significant; a 6-person (3 vs. 3) pilot study with a THC-containing sublingual oil reported a large difference in spasm durations, but the difference persisted in the last 6 weeks, when both groups were using the oil, baseline values were not reported and the full text could not be read. Pure CBD was tested in dystonia only in the uncontrolled 1986 study of 5 patients: improvement, and worsening in two patients with parkinsonian signs. In Huntington’s disease there are three crossover RCTs: pure CBD 10 mg/kg/day (mean about 700 mg/day, 6 weeks; 15 patients not taking neuroleptics) did not differ from placebo on chorea or other measures (p > 0.05); a THC+CBD mouth spray (at most 12 sprays/day, 12 weeks; 26 randomized, 24 completed; primary aim safety) did not differ on motor (p = 0.286), cognitive (p = 0.824), behavioral (p = 1.0) and functional (p = 0.581) scores, with no serious side effects; nabilone (1 or 2 mg; 44 randomized) did not differ on the primary outcome, the UHDRS total motor score (treatment difference 0.86; 95% CI −1.8 to 3.52), while a small difference in favor of nabilone was reported on the chorea subscore (1.68; 0.44 to 2.92) and the Neuropsychiatric Inventory (6.43; 0.2 to 12.66). In the Bilbao 2022 meta-analysis, only the nabilone study was significant in Huntington’s (SMD −0.45; 95% CI −0.79 to −0.11), while pure CBD (SMD 0.18) and the THC+CBD spray (SMD 0.17) were not; because they rested on single studies, they were not graded with GRADE. A 2024 Korean systematic review rates nabilone and the THC+CBD spray as 'possibly ineffective' (Level C) for reducing chorea; in a 2025 review, the nabilone study is the only RCT with a positive result for psychiatric symptoms; the German Society of Neurology's 2023 consensus guideline rates THC and nabilone as 'possibly helpful' for motor symptoms, but in the same paragraph it also writes that the 12-week THC+CBD spray study showed no effect on symptoms. In a single case report, nabilone increased chorea; in an uncontrolled case series of 7 patients (the authors present patients who showed clear improvement), the UHDRS dystonia subscore fell from 12.3 to 8.0 after cannabinoids were started. In dystonia, two 2022 systematic reviews (one with a meta-analysis) showed no benefit: in the 2022 meta-analysis, the effect sizes of the three single studies (one in patients with Huntington’s) ranged from SMD −0.49 to 0.05, and none was significant; there is no review specific to essential tremor or blepharospasm. Real-world data (23 adults with dystonia in Israel; 25 children) reported improvement, but they are uncontrolled and mostly based on self-report. October 2026 search (PubMed, Cochrane, ClinicalTrials.gov, Europe PMC): 9 randomized controlled trials with cannabinoids on this topic (2 in essential tremor, 2 in dystonia, 2 in blepharospasm, 3 in Huntington’s disease), 3 uncontrolled studies (2 prospective, 1 a case series in Huntington’s), 4 systematic reviews and 1 observational study were found; all are in the table below (the Huntington’s section was searched separately on October 30, 2026). There is no Cochrane review specific to cannabinoids; the full text of the 2009 Cochrane review on symptomatic treatments in Huntington’s could not be accessed; on ClinicalTrials.gov there are no studies recruiting patients or with results in the registry that remain unpublished.
Evidence assessment: Pure CBD: Very weak (four small studies, 51 people in total: a single dose in essential tremor, a 12-person pilot study as an add-on to botulinum toxin (Botox) in eyelid spasm, a 5-patient study without a comparison group in dystonia, a 15-person 6-week crossover study in Huntington’s: no difference)
CBD alone
Pure CBD has been tested in four small studies (51 people in total). In 19 patients with essential tremor, a single 300 mg dose of CBD did not reduce tremor more than placebo. In 12 patients with eyelid spasm whose symptoms persisted despite botulinum toxin (Botox), 200 mg of CBD a day for three months shortened eyelid closure time, measured by video, clearly more than placebo; there was no CBD-specific difference in the number or speed of closures, and the small improvement in the doctors' symptom score was not significant. In dystonia, pure CBD was tested only in 1986, in five patients, without a comparison group: improvement was reported, but slowness of movement and tremor increased in two patients with signs of Parkinson’s. In Huntington’s disease, in 15 patients not taking neuroleptic medicines, an average of about 700 mg of pure CBD a day for six weeks did not affect involuntary movements (chorea) or other measures differently from placebo. The strength of evidence is very weak.
Products containing THC
There are four small controlled studies with THC-containing products: a THC and CBD capsule taken for two weeks by seven men with essential tremor and synthetic THC (dronabinol) in nine women with cervical dystonia did not affect tremor or dystonia differently from placebo; in a six-person pilot study in eyelid spasm, spasm attacks were shorter in the group taking a THC-containing under-the-tongue oil, but the difference persisted during the period when both groups were using the oil, and baseline values were not reported. In Huntington’s disease, the mouth spray containing THC and CBD used for 12 weeks in 26 people also showed no difference from placebo in movement, thinking, behavior and daily functioning scores. Nabilone, a synthetic THC-like medicine, showed no difference with a single dose in dystonia; in a 44-person study in Huntington’s, it did not change the overall movement score, and a small improvement in involuntary movements (chorea) was reported, but in a single case report it increased involuntary movements. The improvements reported in 23 adults with dystonia using medical cannabis, in 25 children and in 7 patients with Huntington’s treated with cannabinoids come from studies without a comparison group. THC caused reduced attention, dizziness, unsteadiness and drops in blood pressure.
Evidence: THC and THC+CBD: Very weak (four controlled studies with 6–26 people: no difference in essential tremor, in cervical dystonia, or in Huntington’s disease with a mouth spray used for 12 weeks in 26 people; positive in a 6-person pilot study in eyelid spasm, but the difference between the groups persisted even while both groups were taking the oil; the others uncontrolled or observational). Nabilone, a THC-like medicine, showed no difference with a single dose in dystonia; in Huntington’s, no difference in the overall movement score in a 44-person study, small improvement in chorea (single study)
Dose range in studies
Pure CBD: single dose 300 mg (essential tremor), 200 mg/day (blepharospasm, 3 months), 100→600 mg/day (dystonia, 6 weeks, uncontrolled); THC+CBD capsule (5 mg THC + 100 mg CBD) 1–3 capsules/day (at most 15 mg THC + 300 mg CBD); dronabinol at most 15 mg/day; nabilone single dose 0.03 mg/kg; THC-containing sublingual oil an average of 5–6 drops/day; Huntington’s: pure CBD 10 mg/kg/day (mean about 700 mg/day, 6 weeks), THC+CBD mouth spray at most 12 sprays/day (at most 32.4 mg THC + 30 mg CBD, 12 weeks), nabilone 1 or 2 mg
Starting dose and titration
THC+CBD capsule: from 1 capsule, increased every 2–3 days up to at most 3, 2 weeks stable, stopped by tapering over 1 week (Longardner 2025); pure CBD in dystonia from 100 to 600 mg/day over 6 weeks (Consroe 1986); in blepharospasm, pure CBD at a fixed dose (Silkiss 2023); dronabinol gradually with 2.5 mg tablets (Zadikoff 2011); THC-containing oil individually according to effect and tolerability (Zloto 2022); in Huntington’s, THC+CBD spray up to at most 12 sprays a day (López-Sendón 2016; details could not be read); these are research protocols
These are doses researchers gave under medical supervision; they are not a recommended dose for you. "mg/kg/day" means milligrams per kilogram of body weight per day.
| Study | Participants | Product | Dose and titration | Duration | Result | Source |
|---|---|---|---|---|---|---|
| Silkiss 2023 Double-blind, placebo-controlled, crossover randomized pilot (feasibility) study; single center (US, private eye clinic) | 12 randomized; 12 completed (8 women, 4 men) Adults with adult-onset idiopathic blepharospasm whose symptoms persisted despite regular botulinum toxin injections at the highest tolerated dose (median age 71.5; median 6 years of botulinum treatment); no previous CBD use | Pure CBD oral solution (approved CBD medicine, Epidiolex), under the tongue; placebo: identical-looking inactive oil; both donated by the manufacturer. Botulinum toxin injections continued every 3 months | 200 mg/day (100 mg twice a day) None; a fixed dose deliberately chosen to be low (the authors suggest a dose up to five times higher in a future study) | 6 months: two 3-month periods (CBD and placebo; order assigned at random) | The primary efficacy measures were video-based eyelid movement analysis (number, duration, amplitude and peak velocity of closures). In the CBD period, median eyelid closure duration shortened by 15.8% (−18.35 ms; 95% CI −29.37 to −7.32; p = 0.001 vs. baseline; −4.6% in the placebo period, not significant), and on this measure CBD differed from placebo (p < 0.001); it was the only measure that remained different from placebo after correction for multiple comparisons. Closure amplitude decreased by 19.1% with CBD (p = 0.03), but the difference between CBD and placebo was not significant (p = 0.08). The change in peak closure velocity was similar in the CBD (34.8%) and placebo (33.2%) periods (p = 0.93 between CBD and placebo); there was no significant change in the number of closures. The average 0.5-point reduction in severity and frequency on the Jankovic Rating Scale used by doctors was not statistically significant; the authors write that the study may have been underpowered for the clinical scale. Supported by a blepharospasm research foundation, an eye foundation and a US National Eye Institute (NIH) grant; the manufacturer donated the drug and placebo; the authors report no conflicts of interest Side effects: All 12 people completed the study; no significant side effects; mild stool softening in 1 person | PMID 37606606, doi:10.1167/tvst.12.8.17, NCT04423341, 12 people, no results in the registry) |
| Longardner 2025 Double-blind, placebo-controlled, crossover randomized phase 1b/2 pilot study; single center (US, San Diego) | 7 randomized; 5 completed (the target was 14 people; analysis with 6 people according to the abstract, 7 according to the full text) Adults with essential tremor (all white men; mean age 67; disease duration about 40 years; 1 person was taking a tremor medicine); Parkinson’s and other tremor types were excluded at screening | Capsule by mouth (Tilray TN-CT120 LM, investigational product): 5 mg THC + 100 mg CBD per capsule; identical-looking placebo capsule; both supplied by the manufacturer | 1–3 capsules a day (at most 15 mg THC + 300 mg CBD/day), after breakfast Increase by 1 capsule every 2–3 days as tolerated; 2 weeks at the highest tolerated dose; stopped by tapering over 1 week | Each period: 1 week of dose increase + 2 weeks at the highest tolerated dose + 1 week of tapering; 3-week washout between periods | Primary outcome (tremor amplitude measured by spiral drawing on a tablet): no difference between THC+CBD and placebo (largest amplitude difference −1.02 mm, p = 0.13; mean amplitude p = 0.37; tremor power p = 0.92). On the clinical tremor scale TETRAS, the reduction was 10.30 points in the THC+CBD period and 8.07 points in the placebo period (p = 0.27); no difference in the clinician and patient global impression (p = 0.35); cognitive test score no different (p = 0.47). The largest spiral amplitude fell by about half from baseline in both periods (according to the authors, first-visit nervousness wearing off and getting used to the test). 91.7% of participants and clinicians correctly guessed which period they were in. In some participants, CBD breakdown products were also measured in the blood during the placebo period; the authors write that the 3-week washout may not have been enough. Standing diastolic blood pressure was lower in the THC+CBD period (−4.8 mmHg; p = 0.001). The target number of people was not reached (the product's shelf life expired twice, the pandemic, resource problems); the authors consider the result preliminary. Supported by the International Essential Tremor Foundation, the product's manufacturer (Tilray: product, placebo, regulatory work and financial support), the Center for Medicinal Cannabis Research (CMCR) and the NIH; 1 of the 8 authors declares running another open-label study with CBD supplied by a CBD medicine manufacturer (Jazz Pharmaceuticals) Side effects: Of 101 side effects in total, 66 occurred in the THC+CBD period and 28 in the placebo period. According to the registry results, in the THC+CBD period: reduced attention in 7 of 7 people (0 on placebo), dizziness in 4, sleepiness in 4, unsteadiness in 3, memory problems in 3. 1 serious side effect: brief convulsive fainting (convulsive syncope) on an airplane after taking 3 capsules on an empty stomach, with low blood pressure and a slow pulse at the hospital; discharged the same day and withdrawn from the study; the safety board judged that it may have been drug-related. 1 person could not tolerate the lowest dose. The side effect table in the registry shows 0 serious side effects | PMID 40248111, doi:10.5334/tohm.1005, NCT03805750, PMID 39144396 |
| Santos de Alencar 2021 Double-blind, placebo-controlled, crossover randomized study; single dose (Brazil, Ribeirão Preto) | 19 (10 men, 9 women) Adults with essential tremor whose tremor was not adequately controlled with their usual medicines (mean age 63; mean disease duration 23 years) | Pure CBD by mouth; placebo | Single dose 300 mg | Single dose; two sessions 2 weeks apart; measurements before the dose and 60 and 210 minutes after | No significant difference between CBD and placebo in the arm tremor score on the Fahn-Tolosa-Marin tremor scale, in tremor scores on writing and drawing/water-pouring tasks, or in the doctor's global impression of change; no carryover effect between periods. The authors write that they did not rule out an effect of regular (long-term) use. The full text could not be read: the source of the CBD, funding and this study's declaration of interests could not be verified; of the 6 authors, Crippa and Hallak report in the same group's other publications (e.g., Linares 2019) that they are medical advisors to a CBD company; Crippa also reports that he is an inventor on a patent for a CBD derivative and that their university has an agreement with a pharmaceutical company to develop a synthetic CBD product Side effects: No side effects reported in the abstract (full text could not be read) | PMID 33465546, doi:10.1016/j.parkreldis.2021.01.001 |
| Zloto 2022 Prospective, double-blind, placebo-controlled randomized pilot study: the first 6 weeks placebo-controlled, and in the following 6 weeks both groups used medical cannabis oil (Israel, Sheba Medical Center) | 6 (3 cannabis oil, 3 placebo) Adults with benign essential blepharospasm who had not improved enough with botulinum toxin injections (consecutive patients seen between March 2019 and February 2020) | Medical cannabis oil drops under the tongue; according to one review, 3.2% THC and 0.1% CBD (Bondok 2024, secondary source); placebo oil drops (the abstract says 'cannabis oil drops' for the control group; most likely an inactive oil is meant) | In the last 6 weeks, an average of 6.27 drops a day (first treatment group) and 5.36 drops (first placebo group); amount per drop not in the abstract Increased gradually and individually according to effect and tolerability | 12 weeks (6 weeks controlled + 6 weeks with everyone on the active product) | In the first 6 weeks, the mean duration of spasm attacks was 4.29 minutes in the cannabis oil group and 73.9 minutes in the placebo group (p < 0.01). In the last 6 weeks, while both groups were using cannabis oil, the number of spasms was 61 vs. 94 (p = 0.05) and the mean attack duration 1.77 vs. 8.96 minutes (p < 0.01): the difference between the groups persisted even while both groups were taking the active product. Baseline values and the measurement method are not in the abstract; so it cannot be known how much of the difference in the first period came from the oil. The authors conclude that it may be effective and safe as a second-line option after botulinum toxin; however, there are 3 people in each group and the full text could not be read. 1 of the 10 authors is from an association that supports the spread of medical cannabis (Tikun Olam NGO); the study's declaration of interests is not in PubMed Side effects: Mild: general tiredness, dry mouth, trouble sleeping; no significant eye or systemic side effects were reported | PMID 35067772, doi:10.1007/s00417-021-05533-1, PMID 39629058, PMID 38015317 |
| Zadikoff 2011 Double-blind, placebo-controlled, crossover randomized phase 2a study (most likely Canada, Toronto Western Hospital; from the registry record) | 9 (all women; according to Lim 2017); its likely registry record had planned 38 people Adults with cervical dystonia (mean age 60) | Dronabinol (synthetic THC), by mouth; placebo | With 2.5 mg tablets, at most 3 tablets twice a day (at most 15 mg/day) Gradual increase (details could not be read) | About 8 weeks (two periods; according to Lim 2017 and Bilbao 2022); in the registry record, the primary measure after 3 weeks of active treatment | No significant difference between dronabinol and placebo on a cervical dystonia scale (Toronto Western Spasmodic Torticollis Rating Scale, TWSTRS) or on any secondary measure (Lim 2017 review, PMID 29073741); the same review rated the risk of bias as 'high'. In the Bilbao 2022 meta-analysis, the effect size was SMD 0.05 (95% CI −0.69 to 0.79). Its title speaks of 'failure in a phase IIa randomized controlled trial'. Published in a journal not indexed in PubMed; abstract and full text could not be read; figures from two systematic reviews Side effects: Light-headedness, sleepiness, dry mouth, blurred vision, bitter taste in the mouth, dizziness (Lim 2017 table); frequencies could not be read | doi:10.1016/j.baga.2011.04.002, Basal Ganglia 2011, 1(2):91–95 (not in PubMed, citation from Crossref, NCT00418925, Toronto, principal investigator the article's last author, S. H. Fox, phase 2, crossover, triple-blind, 2.5 mg dronabinol tablets, primary measure TWSTRS, Dystonia Medical Research Foundation as collaborator, 38 people planned, status 'unknown', last updated 2008, no results), the registration number could not be seen in the article |
| Fox 2002 Double-blind, placebo-controlled, crossover randomized study; single dose (United Kingdom) | 15; 2 people were withdrawn because of side effects (Lim 2017 table) Adults with generalized or segmental primary dystonia (aged 28–63, mean 47) | Nabilone (a synthetic cannabinoid similar to THC), by mouth; placebo | Single dose 0.03 mg/kg | Single dose; measurements 60, 120 and 180 minutes after the dose | No significant reduction with nabilone compared with placebo on a dystonia scale (Burke-Fahn-Marsden); 4 patients reported subjective improvement (Lim 2017 review, PMID 29073741; risk of bias 'unclear'). In the Bilbao 2022 meta-analysis, SMD −0.49 (95% CI −1.07 to 0.08; p = 0.09); the authors interpreted this as 'possible benefit'. The rationale for the study was that a basal ganglia region thought to be overactive in dystonia (the globus pallidus) could be calmed by stimulating cannabinoid receptors. Full text could not be read Side effects: 2 patients were withdrawn from the study because of a drop in blood pressure on standing and marked sleepiness (Lim 2017 table) | PMID 11835452, doi:10.1002/mds.1280 |
| Consroe 1986 Open-label pilot study; no control group | 5 Patients with dystonic movement disorders (2 also had parkinsonian signs); they continued their usual medicines | Pure CBD (cannabidiol) by mouth | From 100 mg/day to 600 mg/day Increased from 100 to 600 mg/day over 6 weeks | 6 weeks | Dose-related improvement in dystonia of 20% to 50% was reported in all five patients. In 2 patients who also had parkinsonian signs, slowness of movement (hypokinesia) and resting tremor worsened at doses above 300 mg/day. No control group or blinding; the placebo effect cannot be separated. Supported by the US National Institute of Neurological Disorders and Stroke (NINDS). Full text could not be read Side effects: Mild: low blood pressure, dry mouth, slowed movements (psychomotor slowing), light-headedness, sleepiness | PMID 3793381, doi:10.3109/00207458608985678, The same group's preliminary report: Sandyk 1986, PMID 3749389, letter, no abstract, could not be read) |
| Libzon 2018 Pilot study comparing two products; no placebo group (tagged as a randomized controlled trial in PubMed, and its likely registry entry NCT02470325 is randomized and triple-blind; no details on randomization and blinding in the abstract; the Murni 2023 review counted it as a non-randomized study) | 25 (19 with cerebral palsy; diagnosis breakdown from Murni 2023 Table 1, secondary source) Children aged 1–17 with moderate to severe complex movement disorders in which different types of abnormal movements occur together (Israel, Wolfson Medical Center pediatric movement disorders unit) | Two CBD-rich cannabis oils (5% CBD): with 0.25% THC (CBD:THC 20:1) and with 0.83% THC (6:1) | Not in the abstract (full text could not be read) Not in the abstract | 5 months | Significant improvement in dystonia and muscle stiffness (spasticity), sleep difficulty, pain severity and quality of life was reported in the whole group, regardless of which oil was taken; the dystonia scale and the figures are not in the abstract. Because there was no placebo group, it cannot be known how much of the improvement came from the oil. Very small; 3 of the 8 authors were from the research department of a cannabis company (Tikun Olam) Side effects: Rare: increased seizures in 2 children, behavior change in 2, sleepiness in 1 | PMID 29766748, doi:10.1177/0883073818773028, NCT02470325, 6:1 and 20:1 CBD:THC oils, conditions muscle stiffness and dystonia, 40 people planned, record not updated since 2015, status 'unknown'), match not confirmed |
| Bilbao 2022 Systematic review and meta-analysis of RCTs, separated by drug type (up to October 2021; GRADE) | 152 RCTs (all indications, 12,123 participants); in dystonia, 3 small crossover RCTs (dronabinol, nabilone, nabiximols; each a single study); in Huntington’s, 3 crossover RCTs (nabilone, pure CBD, nabiximols) People with any condition; under the dystonia subheading, patients with dystonia (one being the dystonia measure of a study done in patients with Huntington’s), under the Huntington’s subheading, patients with Huntington’s disease | Dronabinol, nabilone, pure CBD and nabiximols (natural products such as smoked cannabis excluded) | In the dystonia studies, dronabinol at most 15 mg/day, nabilone single dose 0.03 mg/kg, nabiximols 32.4 mg THC + 30 mg CBD/day; in the Huntington’s studies, nabilone 1 or 2 mg, pure CBD 10 mg/kg/day, nabiximols at most 12 sprays/day | From a single dose to 12 weeks in the dystonia studies; 5–12-week periods in the Huntington’s studies | No significant benefit in any of the three studies in dystonia: nabilone SMD −0.49 (95% CI −1.07 to 0.08; p = 0.09; Fox 2002), nabiximols SMD 0 (−0.39 to 0.39), dronabinol SMD 0.05 (−0.69 to 0.79; Zadikoff 2011). The nabiximols data in dystonia come from the dystonia measure of a study done in patients with Huntington’s (López-Sendón 2016). In the Huntington’s analysis (3 crossover RCTs), only nabilone was significant: SMD −0.45 (95% CI −0.79 to −0.11; p = 0.009; Curtis 2009); pure CBD SMD 0.18 (p = 0.48; Consroe 1991) and nabiximols SMD 0.17 (p = 0.4; López-Sendón 2016) were not significant; the difference between subgroups was significant (p = 0.03). Because they rested on single studies, they were not graded with GRADE. Essential tremor and blepharospasm are not among the review's indications; there is no RCT with pure CBD in dystonia Side effects: Across all indications, the chance of any side effect was higher than with placebo (dronabinol OR 2.16; nabilone OR 3.12; pure CBD OR 1.82; nabiximols OR 1.97); no dystonia-specific side effect analysis | PMID 35982439, doi:10.1186/s12916-022-02459-1, PROSPERO CRD42021229932 |
| Oikonomou 2022 Systematic review of cannabinoid RCTs in movement disorders (no meta-analysis) | 7 RCTs in Parkinson’s, 2 in Tourette, 3 in Huntington’s, 2 in dystonia Patients with movement disorders (Parkinson’s, Tourette, Huntington’s, dystonia) | Various cannabinoid products (nabilone and CBD mentioned in the abstract) | Variable | The two RCTs in dystonia failed to show a reduction in dystonia. Of the three RCTs in Huntington’s, only the nabilone study found symptom relief. The abstract does not mention the essential tremor and blepharospasm studies. The authors write that the small and heterogeneous RCTs do not allow reliable conclusions and that more well-designed RCTs are needed. Full text could not be read; which two dystonia studies were included could not be verified (most likely Fox 2002 and Zadikoff 2011) Side effects: No side effect analysis in the abstract | PMID 35859051, doi:10.1007/s00702-022-02529-x | |
| Anis 2023 Single-center, retrospective real-world study: chart review and structured interview; no control group (Israel, Tel Aviv Sourasky Medical Center) | 23 (11 women, 12 men); medical cannabis had been recommended to 36 of the clinic's 125 patients with dystonia Adults with dystonia using licensed medical cannabis (mean age 52.7; 9 generalized, 6 focal, 5 segmental, 2 hemidystonia, 1 multifocal dystonia; in 6, the dystonia was part of Parkinson’s disease) | Licensed medical cannabis: dried flower smoked or inhaled by vaporizing (11), sublingual oil (10), both (2); products averaged 10.6% THC and 8.0% CBD | Average 22.3 g a month; estimated daily THC about 101 mg, CBD about 51 mg (highly variable from person to person) According to the Israeli Ministry of Health guideline (at most 20 g/month at the start); individualized | Average 2.5 years of use (± 2.9) | The average self-reported improvement was 47.5%; 63% in those with generalized dystonia and 32% in those with focal or segmental dystonia (p = 0.04). Those who smoked it reported an average improvement of 78.5%, compared with 21% in those using sublingual oil (p = 0.00033); the reported improvement was linked to the THC proportion of the product and the monthly amount. Satisfaction with pain and with quality of life was 3.8 and 3.6 out of 5. The authors write that because of the small sample, selection bias, and retrospective, one-time self-report, the result needs to be tested in randomized studies Side effects: Dry mouth 65%, sleepiness 43%, dizziness 39%; psychiatric side effects in 6 people (26%): anxiety in 3 (hallucinations in one), worsening mood in 3 (suicidal thoughts in one); improved with a change in treatment (e.g., a product with lower THC) in 5; 3 people (13%) stopped (1 because of side effects, 2 because of lack of effect) | PMID 37456642, doi:10.3389/fneur.2023.1218300 |
| Consroe 1991 Double-blind, placebo-controlled, crossover randomized study | 15 patients evaluated (abstract; 8 men, 7 women according to the Lim 2017 table); according to one review, 18 people were enrolled and 3 male patients left for reasons unrelated to the study after completing weeks 5, 6 and 10 (Bahji 2022, secondary source; full text could not be read) Patients with Huntington’s disease not taking neuroleptic (antipsychotic) medicines (aged 17–66, median 52; Lim 2017 table) | Pure CBD (cannabidiol) by mouth; placebo: sesame oil | 10 mg/kg/day (mean about 700 mg/day); split into two doses a day according to Lim 2017 Not in the abstract (full text could not be read) | Two 6-week periods (CBD and placebo); weekly assessments; according to one review, total duration 15 weeks (Bahji 2022, secondary source) | No significant (p > 0.05) or clinically important difference between CBD and placebo in chorea severity (the Marsden and Quinn chorea severity scale according to Lim 2017), other treatment outcomes or safety measures; according to one review, the median chorea score was 11.5 in the CBD period and 13.7 in the placebo period (p = 0.71; Bahji 2022, secondary source). The weekly mean plasma CBD level was 5.9–11.2 ng/mL and did not change significantly over 6 weeks; in the measurement publication from the same trial, no THC was detected in the blood. The authors write that at this dose and duration CBD did not improve symptoms and had no toxic effect compared with placebo either. Supported by a US Public Health Service (PHS) grant (PubMed). Full text could not be read Side effects: No significant difference from placebo on a cannabis side effect inventory, clinical laboratory tests or other safety measures | PMID 1839644, doi:10.1016/0091-3057(91)90386-g, Plasma CBD measurement publication from the same trial: Consroe 1991, PMID 1666917, 14 patients, half-life about 2–5 days, no THC detected in plasma). The 'preliminary findings' in the abstract most likely belong to the same group's open-label pilot study, not found in PubMed |
| López-Sendón 2016 Double-blind, placebo-controlled, crossover randomized pilot (phase 2) study; single center (Spain, Madrid, Ramón y Cajal University Hospital; from the registry record) | 26 randomized; 24 completed (actual enrollment in the registry 25) Adults with Huntington’s disease: UHDRS motor score 5–50, MMSE above 25, medicines stable for at least 6 weeks; people with a history of psychosis, suicide attempt or substance dependence and those using cannabis products were not included (from the registry record) | Mouth spray containing THC and CBD (nabiximols, Sativex): 2.7 mg THC + 2.5 mg CBD per spray; identical-looking placebo spray | At most 12 sprays a day (at most 32.4 mg THC + 30 mg CBD/day) According to the registry record, from 1 spray a day up to at most 12; details could not be read | Two 12-week periods (September 2011–June 2012; from the registry record) | The primary aim was safety (no serious side effects and no greater worsening on motor, cognitive, behavioral and functional scales during the active period): after period and sequence effects were ruled out, safety and tolerability were confirmed. No difference between THC+CBD and placebo on UHDRS scores: motor p = 0.286, cognitive p = 0.824, behavioral p = 1.0, functional p = 0.581. No significant change in biomarkers in the blood and cerebrospinal fluid (according to the registry record, BDNF, oxidative stress and inflammation markers). The authors suggest testing higher doses, longer treatment or other cannabinoid combinations. The registry record lists the product's manufacturer (GW Pharmaceuticals) as a collaborator; the full text could not be read, and funding and the declaration of interests could not be verified Side effects: No serious side effects or clinical worsening; well tolerated. According to one review, the most common side effects were dizziness and impaired attention (Lim 2017, secondary source); their frequencies could not be read (full text could not be read) | PMID 27159993, doi:10.1007/s00415-016-8145-9, NCT01502046, EudraCT 2010-024227-24, status 'completed', no results in the registry). Conference abstract: García Caldentey 2012, J Neurol Neurosurg Psychiatry 83:A62 (not read) |
| Curtis 2009 Double-blind, placebo-controlled, crossover randomized pilot study | 44 randomized (22 nabilone first, 22 placebo first); according to one review, 7 people dropped out (2 because of serious side effects; Bahji 2022), and in another review's table 37 people were in the analysis (20 and 17; Andriessen 2025) Adults with Huntington’s disease (aged 34–72, mean 52; Lim 2017 table); people with a history of psychosis were not included (Andriessen 2025 table) | Nabilone (a synthetic cannabinoid similar to THC), by mouth; placebo | 1 or 2 mg (abstract); 1–2 mg a day in the reviews Not in the abstract (full text could not be read) | According to two reviews, two 5-week periods, about 15 weeks in total (full text could not be read) | No difference between nabilone and placebo on the primary outcome, the UHDRS total motor score (treatment difference 0.86; 95% CI −1.8 to 3.52). A difference in favor of nabilone on two of the four secondary measures: chorea subscore 1.68 (0.44 to 2.92) and Neuropsychiatric Inventory (NPI) 6.43 (0.2 to 12.66; p = 0.04, Andriessen 2025); no difference on UHDRS cognitive (3.57; −3.41 to 10.55) and behavioral (4.01; −0.11 to 8.13) scores. The chorea difference is a small change of 1–2 points and comes from a single, small, short study; the authors write that a larger and longer RCT is feasible and necessary. Bilbao 2022 calculated this study's Huntington’s result as SMD −0.45 (95% CI −0.79 to −0.11). Tagged in PubMed as 'Research Support, Non-U.S. Gov't' (non-US public or foundation support); its source and the declaration of interests could not be verified because the full text could not be read Side effects: Safe and well tolerated according to the abstract, no psychotic episodes. According to Lim 2017, most often sleepiness and forgetfulness; according to Bahji 2022, 3 serious side effects and 7 dropouts (2 because of serious side effects); in which period these occurred could not be read | PMID 19845035, doi:10.1002/mds.22809, Based on this study, the American Academy of Neurology's 2012 chorea guideline (later retired, PMID 22815556 |
| Andriessen 2025 Systematic review of drug treatment for psychiatric (neuropsychiatric) symptoms in Huntington’s disease (PRISMA; PubMed and the Cochrane Library, last search September 23, 2024; no meta-analysis) | 15 studies (10 RCTs, 5 open-label), 898 patients with Huntington’s disease; among cannabinoids, only the nabilone RCT (Curtis 2009) Patients with Huntington’s disease | Various medicines; as a cannabinoid, only nabilone (a synthetic cannabinoid similar to THC) | Nabilone 1–2 mg/day (Curtis 2009) | Among the RCTs, the nabilone study was the only one to improve the overall psychiatric symptom score: a 6.43-point reduction on the NPI (95% CI 0.2 to 12.66; p = 0.04), larger than the minimal clinically important difference according to the authors; a trend toward improvement in the UHDRS behavioral domain (p = 0.06). Of the other medicines, only fluoxetine showed a small improvement in irritability in one RCT. For irritability, improvement with nabilone in a single case report is mentioned. The authors write that there is no convincing evidence to guide clinical practice for psychiatric symptoms and that larger, multicenter studies are needed. The pure CBD (Consroe 1991) and THC+CBD spray (López-Sendón 2016) studies were not included in the review. No specific funding; the authors report no relevant conflicts of interest Side effects: Side effects are not the subject of the review | PMID 39891411, doi:10.1002/mdc3.14343, PMC11998698 (full text read: Methods, Tables 1 and 3, Discussion) | |
| Shin 2024 Evidence-based systematic review by the Korean Huntington’s Disease Society (PRISMA; PubMed, Web of Science, Embase, KoreaMed, Scopus and Cochrane, up to August 2022; American Academy of Neurology evidence classification, case reports included; no meta-analysis) | 22 symptom headings across motor, psychiatric, cognitive and other domains; for cannabinoids, the nabilone RCT (Curtis 2009), the THC+CBD spray RCT (López-Sendón 2016), case series and case reports Patients with Huntington’s disease | All drug and non-drug treatments; among cannabinoids, nabilone and the THC+CBD mouth spray (referred to in the review as 'cannabidiol oral spray') | No details in the review | For chorea, nabilone and the THC+CBD mouth spray showed no anti-chorea effect; both were rated 'possibly ineffective in reducing chorea' (Level C); the assessment of nabilone cites, along with the 44-person RCT, the single case report in which chorea increased. In cognition, the THC+CBD spray showed no benefit (Level C). For dystonia and apathy, the evidence for cannabinoids is insufficient (Level U); for irritability, case reports and series are positive, but the level of evidence is uncertain (U); in two cases, excessive saliva production decreased with cannabinoids (U). A five-patient nabilone series in a conference abstract reported both improvement in drug-induced parkinsonism-like symptoms and akathisia (inability to sit still). The pure CBD study (Consroe 1991) is not mentioned in the review. The authors report no conflicts of interest; according to a later correction, the work was supported by a hospital research grant Side effects: No cannabinoid-specific side effect analysis; akathisia with nabilone and an increase in chorea in a single case are mentioned | PMID 39117301, doi:10.14802/jmd.24140, PMID 39622192, funding statement only) | |
| Saft 2018 Case series: comparison with the UHDRS before and after starting cannabinoid treatment (no control group, blinding not reported) | 7 Patients with early-onset Huntington’s disease; the authors present patients whose movement symptoms (especially dystonia) improved clearly with cannabinoid treatment; no other medication changes were made during this time (centers in Germany and Austria; from the author addresses) | Cannabinoids; which patient received which product and dose is not in the abstract. The article's keywords mention dronabinol, nabilone and Sativex (a mouth spray containing THC and CBD); the same group's 2023 guideline refers to this series as 'for example THC or dronabinol' | Not in the abstract Not in the abstract | Not in the abstract (full text could not be read) | The UHDRS motor score fell from a mean of 70.9 (SD 25.5) to 60.6 (26.9) (mean change 10.3; 95% CI 6.0 to 14.6; p = 0.018); the dystonia subscore fell from 12.3 (4.0) to 8.0 (3.6) (4.3; 2.3 to 6.3; p = 0.018). The authors write that they observed improvement in self-care, walking, fine motor skills and weight gain, and in some patients less irritability, apathy and excess saliva. There is no comparison group, blinding was not reported, and the authors present patients who showed clear improvement (they may be selected cases); the placebo effect, expectations and the natural fluctuation of the disease cannot be separated, and it cannot be said that the improvement came from cannabinoids. The full text could not be read (the publisher's page required bot verification) Side effects: No side effects reported in the abstract (full text could not be read) | PMID 29562549, doi:10.3233/JHD-170283 |
Reported side effects
- Pure CBD 200 mg/day (3 months): no significant side effects, softer stools in 1 person (Silkiss 2023)
- Pure CBD 100–600 mg/day: low blood pressure, dry mouth, slowed movements, light-headedness, sleepiness; in 2 patients with parkinsonian signs, increased slowness of movement and resting tremor above 300 mg/day (Consroe 1986)
- THC+CBD capsule: 66 of 101 side effects in the active period; reduced attention in 7 of 7 people, plus dizziness, sleepiness, unsteadiness, forgetfulness; convulsive fainting in 1 person (Longardner 2025)
- Nabilone single dose: 2 patients were withdrawn because of a drop in blood pressure on standing and marked sleepiness (Fox 2002)
- Dronabinol: light-headedness, sleepiness, dry mouth, blurred vision, bitter taste, dizziness (Zadikoff 2011; as reported by a systematic review)
- THC-containing sublingual oil: mild tiredness, dry mouth, trouble sleeping (Zloto 2022)
- Medical cannabis (mostly smoked): dry mouth 65%, sleepiness 43%, dizziness 39%, psychiatric side effects 26%; 3 people stopped (Anis 2023)
- CBD-rich, low-THC oils in children: increased seizures in 2 children, behavior change in 2, sleepiness in 1 (Libzon 2018)
- Pure CBD 10 mg/kg/day (about 700 mg/day, 6 weeks, Huntington’s): no difference from placebo on a cannabis side effect inventory or in laboratory tests; no THC detected in the blood (Consroe 1991)
- THC+CBD mouth spray (at most 12 sprays/day, 12 weeks, Huntington’s): no serious side effects or clinical worsening; according to a review, most often dizziness and impaired attention, frequencies could not be read (López-Sendón 2016; Lim 2017)
- Nabilone 1–2 mg (Huntington’s): no psychotic episodes, well tolerated; according to reviews, most often sleepiness and forgetfulness, 3 serious side effects and 7 dropouts (2 because of serious side effects), breakdown by period could not be read (Curtis 2009); increase in involuntary movements in a single case (Müller-Vahl 1999, case report)
Monitoring done in studies
- In a person using a THC-containing product, blood pressure standing and sitting, dizziness, balance and attention should be monitored; in the essential tremor study, standing blood pressure dropped and one person fainted (Longardner 2025)
- In a person with parkinsonian signs, slowness of movement and tremor should be monitored while using CBD (Consroe 1986)
- As of October 2026, no studies with cannabinoids recruiting or planned in essential tremor, dystonia, blepharospasm or Huntington’s disease were found on ClinicalTrials.gov (the only Huntington’s record, NCT01502046, belongs to the published mouth spray study); there are two old records without results in the registry (dronabinol in cervical dystonia, NCT00418925; CBD-rich oils in dystonia and muscle stiffness in children, NCT02470325)
Who should be careful
- Signs of Parkinson’s: in the small 1986 study, at pure CBD doses above 300 mg a day, slowness of movement and resting tremor increased in two patients with signs of Parkinson’s (Consroe 1986)
- Dizziness, unsteadiness and drops in blood pressure with THC-containing products: in the essential tremor study, one participant briefly fainted after taking the product on an empty stomach (Longardner 2025); with nabilone, two patients left the study because of a drop in blood pressure on standing and sleepiness (Fox 2002)
- Psychiatric side effects: anxiety or worsening mood was reported in 26% of patients with dystonia using medical cannabis, and one had suicidal thoughts; most improved after switching to a product with less THC (Anis 2023)
- Children: the only data in children with dystonia come from a 25-child study without a placebo group; seizures increased in two children (Libzon 2018)
- The treatments in use (tremor medicines, botulinum toxin, and the medicines used for involuntary movements and mood in Huntington’s disease) should not be stopped on one's own; in the studies, cannabinoids were tested in addition to them
- Anyone who takes medicines regularly should consult a doctor before starting; the studies on this page did not systematically assess interactions
- Huntington’s disease: in a single case report, nabilone, a THC-like medicine, increased involuntary movements (chorea) (Müller-Vahl 1999); people with a history of psychosis were not included in the controlled studies, and the studies lasted at most 12 weeks, so the safety of long-term use in these patients is not known (Curtis 2009, López-Sendón 2016)
Drug interactions
- The studies on this page did not systematically assess drug interactions; details are in the site's drug interactions section
- In the essential tremor study, people taking tremor medicines were required to have been on a stable dose for at least 6 weeks (Longardner 2025); in the blepharospasm studies, participants continued botulinum toxin injections (Silkiss 2023, Zloto 2022); in the dystonia study, patients continued their usual medicines (Consroe 1986); in Huntington’s, the pure CBD study enrolled patients not taking neuroleptic medicines (Consroe 1991), and the THC and CBD spray study required medicines to have been stable for at least 6 weeks (López-Sendón 2016; registration NCT01502046)
Abbreviations: RCT, randomized controlled trial (a study in which participants are assigned to groups by chance); placebo, an inactive substance; SMD, OR and RR, effect measures used in analyses that pool studies; CYP, liver enzymes that break down medicines.
If you are considering CBD
- Work out the cause of your tremor or muscle contractions with your doctor: essential tremor, tremor due to Parkinson’s disease and tremor caused by medicines are different conditions, and the research on them is separate too.
- Do not stop your tremor medicines or your botulinum toxin (Botox) injections on your own; in eyelid spasm, pure CBD was tested alongside botulinum toxin injections, not instead of them.
- If you have signs of Parkinson’s, tell your doctor; in an old, small study, high-dose pure CBD increased slowness of movement and tremor in these patients.
- Check the product's label and certificate of analysis (COA) and find out whether it contains THC; THC can cause dizziness, reduced attention and unsteadiness, and can affect driving.
- If you are at risk of falling, watch for dizziness when standing up; in the studies, drops in blood pressure and fainting were seen with THC-containing products.
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Bottom line
CBD has been tested in only a few small studies in essential tremor, dystonia, eyelid spasm and Huntington’s disease, so it is not yet known whether it works. In short trials, no clear difference was seen in tremor or in Huntington’s disease; in eyelid spasm, there is a single small study in which CBD added to botulinum toxin (Botox) improved one video-based measure more than placebo, but the doctors' symptom score showed no clear difference. The safest path is to decide without stopping the treatments you use and after talking with the doctor who follows you.
Frequently asked questions
Does CBD oil help essential tremor (shaking)?
Two small controlled studies published up to October 2026 did not show this. A single 300 mg dose of pure CBD in 19 patients in Brazil and a capsule containing THC and CBD used for two weeks in seven patients in the US did not reduce tremor more than a dummy treatment (placebo). Regular, long-term use of pure CBD has never been tested in essential tremor, so it is too early to say anything for certain. The strength of evidence is very weak.
Does CBD or cannabis work for dystonia?
A benefit has not been shown in controlled studies. Two small studies, with synthetic THC (nine people) and with nabilone, a THC-like medicine (15 people), found no difference from placebo in dystonia. Pure CBD was tested in dystonia only in 1986, in five patients, without a comparison group. Patients using medical cannabis describe improvement, but these studies have no comparison group, and the placebo effect cannot be separated out. The strength of evidence is very weak.
Has CBD been tested in eyelid spasm (blepharospasm)?
Yes, in two small studies; both were done in patients who had not improved enough with botulinum toxin (Botox). In a 12-person study, 200 mg of pure CBD a day shortened the duration of eyelid closures more than placebo, but there was no clear difference in the doctors' symptom score. In another, six-person study, spasm attacks were shorter in the group taking a THC-containing cannabis oil; however, because the difference persisted during the period when both groups were using the oil, it is unclear how much of this came from the oil. These are early clues; they need to be confirmed in larger studies. The strength of evidence is very weak.
Can CBD replace botulinum toxin (Botox) injections?
There is no evidence for this. In the pure CBD study in eyelid spasm, participants continued their botulinum toxin (Botox) injections; CBD was tested only in addition to them. In eyelid spasm and cervical dystonia, botulinum toxin injections are an established treatment; do not stop them without talking to your doctor.
If my tremor is due to Parkinson’s, is this page relevant to me?
Tremor due to Parkinson’s disease is different from essential tremor and is covered on the site's separate Parkinson’s page. One finding on this page matters for people with Parkinson’s too: in the small 1986 dystonia study, pure CBD doses above 300 mg a day increased slowness of movement and resting tremor in two patients with signs of Parkinson’s. Tourette syndrome and MS are also covered on separate pages of the site.
Is there an FDA-approved CBD medicine for tremor, dystonia or Huntington’s disease?
No. As of November 2, 2026, the only FDA-approved CBD medicine is Epidiolex, a prescription oral solution for seizures linked to Lennox–Gastaut syndrome, Dravet syndrome and tuberous sclerosis complex in people 1 year and older. Doctors can legally prescribe an approved drug for another use when they judge it medically appropriate (this is called “off-label” use), but Epidiolex hasn’t been approved for tremor, dystonia or Huntington’s disease. CBD oils sold in stores and online aren’t FDA-approved. The FDA hasn’t evaluated them for safety, dose or quality, and when it tested some products, many didn’t contain the amount of CBD the label claimed. If you’re thinking about CBD, talk with your doctor or pharmacist first, especially about the medicines you already take.
Does CBD or cannabis work in Huntington’s disease?
Three small controlled studies done up to October 2026 did not show this. Pure CBD used for six weeks (15 people) and a mouth spray containing THC and CBD used for 12 weeks (26 people) did not affect symptoms differently from a dummy treatment (placebo). Nabilone, a synthetic THC-like medicine, did not change the overall movement score in a 44-person study; a small improvement in involuntary movements (chorea) and psychiatric symptoms was reported, but this is a preliminary finding from a single small study, and in a single case report nabilone increased involuntary movements. Do not stop the medicines you use for involuntary movements or mood without talking to your doctor. The strength of evidence is very weak.
References
Show 17 references
- Silkiss 2023. Double-blind, placebo-controlled, crossover randomized pilot (feasibility) study; single center (US, private eye clinic). PMID 37606606, doi:10.1167/tvst.12.8.17, NCT04423341, 12 people, no results in the registry)
- Longardner 2025. Double-blind, placebo-controlled, crossover randomized phase 1b/2 pilot study; single center (US, San Diego). PMID 40248111, doi:10.5334/tohm.1005, NCT03805750, PMID 39144396
- Santos de Alencar 2021. Double-blind, placebo-controlled, crossover randomized study; single dose (Brazil, Ribeirão Preto). PMID 33465546, doi:10.1016/j.parkreldis.2021.01.001
- Zloto 2022. Prospective, double-blind, placebo-controlled randomized pilot study: the first 6 weeks placebo-controlled, and in the following 6 weeks both groups used medical cannabis oil (Israel, Sheba Medical Center). PMID 35067772, doi:10.1007/s00417-021-05533-1, PMID 39629058, PMID 38015317
- Zadikoff 2011. Double-blind, placebo-controlled, crossover randomized phase 2a study (most likely Canada, Toronto Western Hospital; from the registry record). doi:10.1016/j.baga.2011.04.002, Basal Ganglia 2011, 1(2):91–95 (not in PubMed, citation from Crossref, NCT00418925, Toronto, principal investigator the article's last author, S. H. Fox, phase 2, crossover, triple-blind, 2.5 mg dronabinol tablets, primary measure TWSTRS, Dystonia Medical Research Foundation as collaborator, 38 people planned, status 'unknown', last updated 2008, no results), the registration number could not be seen in the article
- Fox 2002. Double-blind, placebo-controlled, crossover randomized study; single dose (United Kingdom). PMID 11835452, doi:10.1002/mds.1280
- Consroe 1986. Open-label pilot study; no control group. PMID 3793381, doi:10.3109/00207458608985678, The same group's preliminary report: Sandyk 1986, PMID 3749389, letter, no abstract, could not be read)
- Libzon 2018. Pilot study comparing two products; no placebo group (tagged as a randomized controlled trial in PubMed, and its likely registry entry NCT02470325 is randomized and triple-blind; no details on randomization and blinding in the abstract; the Murni 2023 review counted it as a non-randomized study). PMID 29766748, doi:10.1177/0883073818773028, NCT02470325, 6:1 and 20:1 CBD:THC oils, conditions muscle stiffness and dystonia, 40 people planned, record not updated since 2015, status 'unknown'), match not confirmed
- Bilbao 2022. Systematic review and meta-analysis of RCTs, separated by drug type (up to October 2021; GRADE). PMID 35982439, doi:10.1186/s12916-022-02459-1, PROSPERO CRD42021229932
- Oikonomou 2022. Systematic review of cannabinoid RCTs in movement disorders (no meta-analysis). PMID 35859051, doi:10.1007/s00702-022-02529-x
- Anis 2023. Single-center, retrospective real-world study: chart review and structured interview; no control group (Israel, Tel Aviv Sourasky Medical Center). PMID 37456642, doi:10.3389/fneur.2023.1218300
- Consroe 1991. Double-blind, placebo-controlled, crossover randomized study. PMID 1839644, doi:10.1016/0091-3057(91)90386-g, Plasma CBD measurement publication from the same trial: Consroe 1991, PMID 1666917, 14 patients, half-life about 2–5 days, no THC detected in plasma). The 'preliminary findings' in the abstract most likely belong to the same group's open-label pilot study, not found in PubMed
- López-Sendón 2016. Double-blind, placebo-controlled, crossover randomized pilot (phase 2) study; single center (Spain, Madrid, Ramón y Cajal University Hospital; from the registry record). PMID 27159993, doi:10.1007/s00415-016-8145-9, NCT01502046, EudraCT 2010-024227-24, status 'completed', no results in the registry). Conference abstract: García Caldentey 2012, J Neurol Neurosurg Psychiatry 83:A62 (not read)
- Curtis 2009. Double-blind, placebo-controlled, crossover randomized pilot study. PMID 19845035, doi:10.1002/mds.22809, Based on this study, the American Academy of Neurology's 2012 chorea guideline (later retired, PMID 22815556
- Andriessen 2025. Systematic review of drug treatment for psychiatric (neuropsychiatric) symptoms in Huntington’s disease (PRISMA; PubMed and the Cochrane Library, last search September 23, 2024; no meta-analysis). PMID 39891411, doi:10.1002/mdc3.14343, PMC11998698 (full text read: Methods, Tables 1 and 3, Discussion)
- Shin 2024. Evidence-based systematic review by the Korean Huntington’s Disease Society (PRISMA; PubMed, Web of Science, Embase, KoreaMed, Scopus and Cochrane, up to August 2022; American Academy of Neurology evidence classification, case reports included; no meta-analysis). PMID 39117301, doi:10.14802/jmd.24140, PMID 39622192, funding statement only)
- Saft 2018. Case series: comparison with the UHDRS before and after starting cannabinoid treatment (no control group, blinding not reported). PMID 29562549, doi:10.3233/JHD-170283
Points that could not be verified from the full text
- The journal of the dronabinol study in cervical dystonia (Zadikoff 2011) is not indexed in PubMed; its abstract and full text could not be read. The number of people, duration, dose and result were taken from two systematic reviews (a 2017 review and Bilbao 2022). The principal investigator of the NCT00418925 record on ClinicalTrials.gov is the article's last author; the drug, design and scale in the record are also the same as in the article. Still, because the registration number could not be seen in the article, the match is not certain.
- The full text of the THC-containing oil study in blepharospasm (Zloto 2022) could not be read. The product's content (3.2% THC, 0.1% CBD) comes from a review's table; the design described in the abstract (the control group using 'cannabis oil drops' and both groups taking the active product in the last 6 weeks) is not clear without the full text.
- The full texts of the single-dose CBD study in essential tremor (Santos de Alencar 2021), the nabilone study (Fox 2002), the 1986 dystonia study, the 2022 movement disorders review (Oikonomou 2022) and the children's study (Libzon 2018) could not be read; the figures are from abstracts and reviews.
- In the THC and CBD capsule study (Longardner 2025), the article reports one serious side effect (convulsive fainting), while the results table on ClinicalTrials.gov shows 0 serious side effects. The number of people analyzed is 6 in the abstract and 7 in the full text.
- The full texts of the studies in the Huntington’s section could not be read: the pure CBD study (Consroe 1991), the nabilone study (Curtis 2009), the THC and CBD spray study (López-Sendón 2016), the seven-patient case series (Saft 2018) and the case report in which nabilone increased chorea (Müller-Vahl 1999; no abstract, only the title was read). For the nabilone study, the period length, the number of people analyzed and the serious side effects, and for the pure CBD study, the chorea scale, the number of people enrolled (18 according to one review; the abstract evaluates 15 patients) and the patients who withdrew were taken from the tables of systematic reviews. The type and dose of cannabinoids used in the case series are not in the abstract; the article's keywords mention synthetic THC (dronabinol), nabilone and the mouth spray containing THC and CBD, and it is not known which patient took which. The full text of the 2009 Cochrane review on symptomatic treatments in Huntington’s could not be accessed; whether it covers cannabinoid studies could not be verified.
Research history
Here we record what changed on this page, when and why, with dates. The newest change is at the top.
In the eyelid spasm study, it was corrected that the closure duration is a median, not an average, and that the 16% shortening is relative to baseline (Silkiss 2023, PMID 37606606, full text). The evidence summary now states that only one of the two 2022 reviews is a meta-analysis (Oikonomou 2022, PMID 35859051, abstract; Bilbao 2022, PMID 35982439, full text). In the Anis 2023 row, it was clarified that 78.5% and 21% are average improvements, not group proportions (PMID 37456642, full text). The conclusion and the evidence level did not change.
Page published. This first assessment reviewed 17 studies.