What does the research say?
Six studies have compared cannabis products with a dummy treatment (placebo) in Tourette syndrome, with participants assigned to groups at random; about 170 people took part in total, and all of them used THC-containing products. The largest was done in Germany with 97 adults: a prescription mouth spray containing roughly equal amounts of THC and CBD (nabiximols) was used for 13 weeks. The share of people whose tic score fell by at least a quarter (25%) was 21.9% in the spray group and 9.1% in the placebo group; the difference was not statistically significant. The study plan had defined 'response' as a reduction of at least 30%; by that measure the rates were 12.5% versus 3.0%, and again the difference was not significant. Some additional measures showed a trend toward improvement in tics, depression and quality of life; subgroup findings suggesting clearer improvement in men, in people with severe tics and in people with attention-deficit/hyperactivity disorder (ADHD) are only hints.
In a study in Australia of 22 adults with severe Tourette syndrome, everyone took an oil containing THC and CBD for 6 weeks and a placebo for 6 weeks. On a 50-point tic scale, scores fell by an average of 8.9 points during the oil period and 2.5 points during the placebo period, and the difference was statistically significant; however, 8 of the 22 people had slowed thinking, forgetfulness or trouble concentrating during the oil period. In two small studies with pure THC in Germany in the early 2000s (12 and 24 people), fewer tics were seen only on some scales; based on these two studies, a Cochrane review (2009) found the evidence insufficient.
In a study in Canada with 12 adults (9 completed), participants used three kinds of vaporized marijuana (THC-rich, equal THC and CBD, CBD-rich) and a placebo, once each on different days. On the main measure, a video-based tic assessment, no product made a clear difference; the THC-rich product did better than placebo on the urge before tics and on feelings of distress, while no clear benefit was reported for the CBD-rich product. Blood THC levels were linked to improvement, but CBD levels were not. Most participants could tell whether they had received marijuana or placebo; this can make results look better than they are.
Reviews that pool studies reach different conclusions. A 2026 meta-analysis pooling cannabinoid studies in mental health conditions found a reduction in tic severity compared with placebo, but rated the certainty of the evidence as low for most outcomes (the abstract does not make clear how many studies and which products this result is based on); another meta-analysis published the same year, covering adults, found a negligible effect in Tourette syndrome and rated the certainty as very low. The large improvement in a 2026 meta-analysis specific to Tourette syndrome compares the same people's scores before and after treatment; it is not a difference versus placebo, and it also includes uncontrolled studies. The American Academy of Neurology's 2019 guideline gave 'low confidence' that THC reduces tics and 'high confidence' to behavioral therapy for tics, and wrote that cannabis-based medicines should be avoided in children and adolescents; the European Tourette guideline (2022) lists cannabis-based medicines among options that may be considered only when other treatments have not helped.
Studies without a comparison group (one mostly with smoked or vaporized medical cannabis, the other with THC combined with a fatty acid derivative called palmitoylethanolamide) reported tic scores falling by roughly 20% to 40% over 12 weeks. In clinic records, patients described clear relief of their tics; however, in a 70-patient registry run by a cannabis company, there was no significant improvement in whether tics were present or how often they occurred; quality of life and work status improved. In people who used it for years, the THC dose rose every year; this suggests that tolerance may develop. Studies of this kind cannot separate the placebo effect from the natural waxing and waning of tics.
In children and teens (ages 12–18) there are only two small pilot studies; both were done in Australia by the same research group, with an oil containing 10 mg THC and 15 mg CBD per milliliter. In the placebo-controlled one, 7 of 10 teens completed the study; its aim was to test whether such a study was feasible: after 10 weeks, 3 teens were rated 'much improved' during the oil period and 1 during the placebo period, and the most common side effect was dizziness. According to an editorial assessing this study, no statistical test of effectiveness was done, the improvement in tic scores was very small, and one teen was rated 'much worse' during the oil period. In the other study, which had no comparison group, tic and quality-of-life scores improved. In Israel, more than half of 165 children under 12 with Tourette syndrome who were prescribed medical cannabis oil (mostly CBD-rich, but almost all also containing more or less THC) stopped treatment within the first three months; this registry did not measure effectiveness. The American Academy of Neurology guideline (2019) says cannabis-based medicines should be avoided in children and adolescents, because the evidence is limited and exposure to cannabis in adolescence is linked to possible harms to thinking and mood in adulthood. An expert who runs a pediatric Tourette clinic in Canada also wrote that great caution is needed, pointing out that in these two studies having tried behavioral therapy first was not a requirement for taking part (in the Sydney study, 4 of the 10 teens had not received behavioral treatment) and that regular THC use in adolescence is linked to a risk of psychosis.
Strength of evidence: ○○○○ Insufficient 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
The most common side effects with THC-containing products were dry mouth, tiredness, sleepiness and dizziness. In the study of adults with severe Tourette syndrome, 8 of 22 people had slowed thinking, forgetfulness and trouble concentrating during the THC and CBD oil period. In a study without a comparison group, 6 of 15 people reported mental side effects such as a changed sense of time, confusion or trouble concentrating; three people had worsening anxiety, panic attacks or obsessive-compulsive symptoms. In the largest study (97 people, 13 weeks), side effects occurred in 95% of the mouth spray group and 79% of the placebo group; the clearest difference was in 'feeling strange' (41% versus 3%), a serious side effect occurred in 1 person in each group, and 5 of 64 people versus 1 of 33 stopped because of side effects. In the 16-person study testing THC combined with palmitoylethanolamide, anxiety (11 people), forgetfulness (10) and suspiciousness (paranoia; 6) were also recorded.
Attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD) and anxiety are common in people with Tourette syndrome, so many of them also take other medicines. The Tourette studies did not specifically examine drug interactions. CBD can slow the breakdown of some medicines in the body; this matters for people who take medicines regularly.
Interactions with medicines used for this condition
Interactions reported for these medicines in peer-reviewed publications and official prescribing information. A medicine that is not listed can still interact with CBD; tell your doctor about every medicine you take.
| Medicine | Importance | Warning | Source |
|---|---|---|---|
| Aripiprazole (Abilify, Abizol, Aripa), Other antipsychotics (haloperidol, etc.) (Norodol) | Information | Antipsychotics: No published study has measured antipsychotic blood levels with CBD. In schizophrenia studies, CBD (600–1000 mg a day) added for 6 weeks to the antipsychotic being taken was generally well tolerated; in one study, drowsiness was more common in those taking CBD. Drowsiness may increase when they are taken together; tell your doctor. | PMID 29241357, PMID 29619533, FDA Epidiolex label §7.4 (05/2026) |
To check interactions with the medicines you take: CBD drug interaction checker.
How was CBD used in studies?
Doses used in the studies varied widely by product. In the 6-week study with pure THC, the dose was raised gradually using 2.5 and 5 mg capsules, up to a maximum of 10 mg a day (study dose; not a personal recommendation). With the mouth spray containing THC and CBD, people started with 1 spray a day and increased, depending on the person, to a maximum of 12 sprays within 4 weeks; that is at most 32.4 mg THC and 30 mg CBD a day (study dose; not a personal recommendation). In adults with severe Tourette syndrome, the oil containing THC and CBD (5 mg THC and 5 mg CBD per milliliter) was started at 1 mL a day and increased by 1 mL a week up to a maximum of 4 mL (study dose; not a personal recommendation). In the studies with teens, the oil contained 10 mg THC and 15 mg CBD per milliliter; it was started at 1 mg THC a day and increased, based on body weight, to a maximum of 10 or 20 mg THC (study dose; not a personal recommendation).
In these studies, the dose was adjusted gradually over several weeks according to the research plan, and it was lowered or moved to the evening when side effects occurred. A CBD-dominant product was tested only as a single inhaled dose; there is no dose of oral CBD oil used in Tourette studies.
Study details (for health professionals)
All six randomized controlled trials of cannabinoids in Tourette syndrome and chronic tic disorders used THC. The largest (CANNA-TICS; 97 adults, mouth spray containing THC and CBD, 13 weeks) did not show superiority on the primary outcome: at least a 25% reduction in tic score in 21.9% versus 9.1% (p = 0.076; results in the EU clinical trials register); the protocol had set the response threshold at 30%, according to the register the 25% threshold was set during a blinded data review before the groups were unblinded, and with the 30% threshold the difference was also not significant (12.5% versus 3.0%; p = 0.063); secondary measures showed a trend toward improvement, and at one site 17% of participants asked afterward said they had found out which group they were in. In a crossover study of 22 adults with severe Tourette syndrome, an oil containing THC and CBD lowered the tic score more than placebo (8.9 versus 2.5 points; p = 0.008), but 8 people had cognitive side effects. Two small studies with pure THC in 2002 and 2003 (12 and 24 people) reported reductions on some scales; based on these two, a Cochrane review (2009) found the evidence insufficient, and it has not been updated since. In the 12-person study testing single doses of inhaled marijuana, there was no difference on the primary measure; the THC-rich product did better on secondary measures (urge before tics, distress, overall impression), no benefit was reported for the CBD-rich product, and most participants could tell the product from placebo. In teens (ages 12–18) there are only two pilot studies of 10 people each: one a placebo-controlled crossover feasibility study (according to an editorial, no statistical test of effectiveness was done), the other uncontrolled. Meta-analyses conflict: a 2026 meta-analysis covering 54 RCTs in mental health conditions found a reduction in tic severity (the abstract does not make clear how many studies and which products it is based on; certainty low for most outcomes); another 2026 meta-analysis covering adults found a negligible effect in Tourette syndrome (certainty mostly very low); a 2026 meta-analysis specific to Tourette syndrome compared only before and after treatment. The American Academy of Neurology's 2019 guideline, based on two older pure-THC studies, gave THC 'low confidence', counted cannabis-based medicines as an option that may be considered only in adults who have not improved with other treatments, and recommended avoiding them in children and adolescents and not using them in pregnancy, breastfeeding and psychosis; the European Tourette guideline (2022) lists cannabis-based medicines among options that may be considered only in treatment-resistant cases and recommends education and behavioral therapy as first-line treatment. Uncontrolled studies and clinic records (10–98 people) reported improvement in tics and quality of life; in a 70-person registry there was no significant improvement in tics, and in long-term users the THC dose rose from year to year; in Israel, more than half of children under 12 with Tourette syndrome who were prescribed medical cannabis oil stopped within the first three months. There are no controlled studies with oral CBD oil. October 2026 search (PubMed, Cochrane, ClinicalTrials.gov, EU clinical trials register, Europe PMC): 6 randomized controlled trials of cannabinoids on this topic (177 randomized participants; about 170 people, because two older studies shared patients; all with THC-containing products, one of which also had a CBD-dominant arm), 3 uncontrolled prospective studies, 5 systematic reviews and meta-analyses (1 Cochrane, 1 the evidence review behind the American Academy of Neurology guideline), 1 clinical guideline and 4 observational studies were found; all are in the table below. There is one RCT planned with 60 people whose results were never published (THC and palmitoylethanolamide; according to the EU register, terminated early in Germany in 2019); no studies from Turkey were found.
Evidence assessment: Pure CBD: Insufficient (no studies with CBD oil; CBD-dominant inhaled marijuana was tested only as a single dose, in a 12-person study)
CBD alone
There are no controlled studies of pure CBD or oral CBD oil in Tourette syndrome. CBD-dominant vaporized marijuana (which also contains a small amount of THC) was tested only as a single dose given once, in a study of 12 adults (9 completed); no clear difference from placebo in tics was reported. Positive results seen with products that also contain CBD cannot be separated from THC: in studies that measured blood levels, improvement was linked to THC and its breakdown products, not to CBD. In Israel, most of the products given to children under 12 with Tourette syndrome who were prescribed medical cannabis oil were CBD-rich, but almost all of them also contained THC (96% of the first bottles dispensed); more than half of these children stopped treatment within the first three months, and the registry did not measure effectiveness.
Products containing THC
The results of six small controlled studies (about 170 people in total) with pure THC, a mouth spray or oil containing THC and CBD, and inhaled marijuana are not consistent: in a 22-person crossover study, the tic score fell more with the THC and CBD oil than with placebo; in two small studies with pure THC, a reduction was seen only on some scales; in the largest study, with 97 people (mouth spray, 13 weeks), the share of people whose tics fell by at least a quarter was 21.9% versus 9.1%, but the difference was not statistically significant (nor was it with the 30% threshold in the study plan); with a single dose of inhaled marijuana there was no difference on the main measure. In teens there are only two pilot studies of 10 people each. Of two meta-analyses in 2026, one found fewer tics and the other a negligible effect; the certainty of the evidence is low or very low. THC caused slowed thinking, dizziness and sleepiness; in one study most participants could tell which group they were in.
Evidence: THC and THC+CBD: Weak (6 small controlled studies, 10–97 people; the largest did not show superiority on the main measure; meta-analyses conflict, certainty low to very low; only two pilot studies in children and adolescents)
Dose range in studies
Pure THC single dose 5–10 mg and at most 10 mg/day (6 weeks); nabiximols 1–12 sprays/day (at most 32.4 mg THC + 30 mg CBD); THC+CBD oil (5+5 mg/mL) 1–4 mL/day (at most 20 mg THC + 20 mg CBD); in teens THC+CBD oil (10+15 mg/mL) at most 10 or 20 mg THC/day; dronabinol at most 10 mg/day + palmitoylethanolamide 800 mg/day; inhaled marijuana single dose 0.25 g; no studies with CBD oil
Starting dose and titration
Nabiximols: started at 1 spray a day and raised, depending on the person, to at most 12 over 4 weeks (CANNA-TICS protocol); THC+CBD oil: from 1 mL/day, increased by 1 mL a week to at most 4 mL (Mosley 2023); in teens from 1 mg THC/day to 5 or 10 mg over about 3 weeks, and if there was no response, increased for 3 more weeks to 10 or 20 mg (Eapen 2025); dronabinol from 2.5 mg to 10 mg over 1 week (Bloch 2021); 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 |
|---|---|---|---|---|---|---|
| Müller-Vahl 2023 (CANNA-TICS) Multicenter, double-blind, placebo-controlled, parallel-group phase 3b RCT (2:1 randomization; Germany) | 97 randomized (64 nabiximols / 33 placebo); 72 completed (48 / 24) Adults with Tourette syndrome or chronic motor tic disorder (mean age 37.4 according to the Serag 2024 table; 73 men, 24 women); tic and co-occurring condition medicines stable for at least 30 days | Nabiximols (Sativex), oromucosal spray; each spray 2.7 mg THC + 2.5 mg CBD; placebo spray | 1–12 sprays a day (at most 32.4 mg THC + 30 mg CBD/day); no target dose, individualized Per protocol, started at 1 spray a day and increased by 1 spray every 2 days for the first 4 days, then every day (slower increases allowed); 4 weeks of adjustment, 9 weeks of stable dose; stopped without tapering at the end | 13 weeks (4 weeks dose adjustment + 9 weeks stable dose) | Primary outcome (at least a 25% reduction in YGTSS total tic score at week 13): 14/64 (21.9%) with nabiximols, 3/33 (9.1%) with placebo; risk difference 12.8 percentage points (95% CI −1.3 to 26.9; p = 0.076), superiority not shown. In the protocol (2020) and in the 2021 statistics paper, the response threshold was at least a 30% reduction; according to the results in the EU clinical trials register, the 25% threshold was set during a blinded data review before the groups were unblinded, and with the original 30% threshold the response was 8/64 (12.5%) versus 1/33 (3.0%) (p = 0.063; again not significant). On secondary measures, a trend toward improvement in tics, depression and quality of life; no difference in premonitory urge (as reported by Czech 2026). Clearer improvement in men, in those with severe tics and in those with ADHD comes from exploratory subgroup analyses (difference not significant in the ADHD subgroup; as reported by Czech 2026). During the pandemic, assessments moved to video calls (Lasch 2021). Of the 54 participants at the Hannover site, 9 of the 53 reached (17%) reported having found out which group they were in (7 during treatment; through a THC urine test or by accident). Funded by the German Research Foundation (DFG); the drug and placebo were supplied by the manufacturer (GW Pharma); the driving substudy was supported by the company holding the drug's European marketing rights (Almirall). According to the study's conflict-of-interest statement, 2 of 16 authors report ties with cannabinoid companies: the principal investigator declares research support from companies including the drug's manufacturer and marketing-rights holder, consulting, advisory board and speaker fees from many cannabis companies, and shares in a pharmaceutical company; another author declares research support from companies including one developing a THC-containing drug (Therapix) Side effects: According to the results in the EU clinical trials register, a serious side effect occurred in 1 person in each group (worsening tics in the nabiximols group, not considered drug-related). Any side effect 61/64 (95.3%) with nabiximols, 26/33 (78.8%) with placebo; most common were 'feeling strange' (40.6% versus 3.0%), dizziness (35.9% versus 33.3%), tiredness (29.7% versus 24.2%), dryness at the application site in the mouth (18.8% versus 9.1%) and fatigue (12.5% versus 3.0%); palpitations 5/64 versus 0, panic attacks 4/64 versus 1/33; stopping because of side effects 5/64 versus 1/33. In the driving substudy (64 people), the share judged fit to drive rose from 55.8% to 71.8% with nabiximols and fell from 66.7% to 52.6% with placebo (risk difference 0.17; 95% CI −0.08 to 0.43) | PMID 36878177, doi:10.1016/j.psychres.2023.115135, NCT03087201, no results in the registry), EU clinical trials register EudraCT 2016-000564-42 (results posted on December 31, 2023: primary outcome, dropouts, PMID 33324255, PMID 33594741, PMID 38265476, PMID 36213751 |
| Mosley 2023 Double-blind, placebo-controlled, randomized crossover study (Australia) | 22 (8 women) Adults with severe Tourette syndrome | Oral oil: 5 mg THC + 5 mg CBD per mL; placebo, an inactive oil with matched excipients | From 1 mL/day up to at most 4 mL/day (at most 20 mg THC + 20 mg CBD/day), in divided doses Increased by 1 mL a week if the tic score fell by less than 2 points (ANZCTR record) | 6 weeks active + 6 weeks placebo (order assigned at random; 4-week washout between) | The YGTSS total tic score (0–50) fell at week 6 by 8.9 (± 7.6) points in the active period and 2.5 (± 8.5) points in the placebo period; in the mixed model, the treatment × visit interaction was −2.28 (95% CI −3.96 to −0.60; p = 0.008). On secondary measures, tic-related impairment, anxiety and obsessive-compulsive symptoms were reported to possibly decrease. The plasma level of a THC breakdown product (11-carboxy-THC) was linked to the primary outcome; the link weakened when an outlier was removed. Funded by a hospital research institute and a university initiative funded by philanthropic donation Side effects: In the active period the most common was cognitive difficulty (slowed thinking, forgetfulness, trouble concentrating; 8 people); in the placebo period the most common was headache (7 people) | PMID 38320199, doi:10.1056/EVIDoa2300012, ANZCTR ACTRN12618000545268 (target 24, enrolled 22, first participant March 2019, last data April 2022, funding Wesley Medical Research Institute, collaborator Lambert Initiative) |
| Abi-Jaoude 2023 Double-blind, placebo-controlled, randomized crossover pilot study; single dose of each product (Canada, Toronto) | 12 randomized; 9 completed (15 people enrolled according to the registry) Adults with Tourette syndrome (ages 18–65) | Vaporized marijuana: 10% THC; 9% THC + 9% CBD; 13% CBD (14% CBD and 0.6% THC according to the registry); placebo (THC and CBD below 0.3%) | Single dose of 0.25 g per session | Single dose, 4 sessions 2 weeks apart; 5 hours of monitoring per session | Primary outcome (video-based modified Rush tic scale): no significant difference versus placebo for any product. On secondary measures, the 10% THC product (and, to a lesser extent, the THC+CBD product) did better than placebo on premonitory urge (PUTS), distress (SUDS) and clinical global impression (CGI-I); no significant benefit was reported for the CBD-rich product (abstract). Plasma levels of THC and its breakdown products were linked to improvement on all measures, but CBD levels were not. Most participants correctly guessed whether they had received marijuana or placebo. In the registry, the study appears as terminated because recruitment took too long Side effects: Side effects more common than placebo with all marijuana products; most with the 10% THC product, especially cognitive and psychomotor effects | PMID 36040329, doi:10.1089/can.2022.0091, NCT03247244, Toronto, January 2018–January 2020, terminated: recruitment took long, no results in the registry) |
| Efron 2025 Double-blind, placebo-controlled, randomized crossover phase 1/2 pilot (feasibility) study (Australia, Melbourne) | 10 randomized; 7 completed Adolescents aged 12–18 with Tourette syndrome (mean age 14.8; 50% male) | Oral oil: 10 mg THC + 15 mg CBD per mL (in mint-flavored medium-chain triglyceride oil); matched placebo | By weight: under 50 kg at most 10 mg THC/day, 50 kg and over at most 20 mg THC/day According to the registry, started at 0.1 mL (1 mg THC) a day and increased in 0.1 mL steps to 0.5 mL (under 50 kg) or 1 mL (50 kg and over) by day 21; response assessed on day 29, and if no response, increased to 1 mL or 2 mL by day 49 | 10 weeks per period; 4 weeks between (1-week taper + 3-week washout) | The primary outcomes were feasibility: 100% of visits and blood tests and 97.6% of questionnaires were completed; adherence to the medicine was at an acceptable level in 63.6% of the teens; families found the study schedule acceptable. At week 10, on the clinical global impression (CGI-I), 3 teens were rated 'much improved' during the oil period and 1 during the placebo period. According to an editorial assessing the study (Abi-Jaoude 2026; the full text of the study could not be read), no statistical test of effectiveness was done, the numerical improvement in tic scores was very small, and one teen was rated 'much worse' during the oil period (none on placebo). The authors write that an adequately powered study is needed for effectiveness Side effects: Most common was dizziness (67%); no serious side effects; 2 teens stopped because of side effects (1 during the oil period, 1 during the placebo period), and 1 was lost to follow-up | PMID 40082070, doi:10.1089/can.2024.0188, NCT05184478, May 2022–January 2024, drug made by Cann Group, no results in the registry). The same team's uncontrolled study: Eapen 2025. Assessment: Abi-Jaoude 2026 editorial, PMID 41556111, the author led the Abi-Jaoude 2023 study in adults, no declared conflicts) |
| Müller-Vahl 2003 Double-blind, placebo-controlled, parallel-group RCT (Germany, Hannover) | 24 randomized; 7 dropped out or were withdrawn (1 because of side effects) Patients with Tourette syndrome (DSM-III-R; mean age 33 according to the Serag 2024 table) | Oral pure THC (2.5 and 5 mg gelatin capsules) | At most 10 mg THC/day Gradual increase to a target of 10 mg/day (details not in the abstract) | 6 weeks (+ follow-up after the drug was stopped) | On clinician scales (TS-CGI, STSSS, YGTSS, video scale), a significant difference versus placebo (p < 0.05) or a near-significant trend (p < 0.10) at some treatment visits; on the patient-completed tic list (TSSL), a significant difference on 10 days between days 16 and 41; p = 0.037 in the analysis of variance. According to Cochrane 2009, the improvement was small and seen only on some measures; the number of dropouts and withdrawals was high, and the reported analyses were done only with patients who stayed in the study. The American Academy of Neurology review (2019) rated the study Class III on its four-tier evidence classification Side effects: No serious side effects; 1 patient stopped because of side effects. In the same trial's cognitive safety analysis, no worsening was seen in learning, memory or divided attention | PMID 12716250, doi:10.4088/jcp.v64n0417, Cognitive safety publication of the same trial: Müller-Vahl 2003, PMID 12589392 |
| Müller-Vahl 2002 Double-blind, placebo-controlled, randomized crossover single-dose study (Germany) | 12 Adults with Tourette syndrome | Oral pure THC | Single dose of 5, 7.5 or 10 mg | Single dose (in each period) | On the patient-completed list (TSSL), tics (p = 0.015) and obsessive-compulsive behaviors (p = 0.041) decreased more than with placebo; on clinician ratings only the 'complex motor tics' subscore was significant (p = 0.015), with trends for motor tics, simple motor tics and vocal tics (p = 0.065–0.093). Improvement in tics was linked to the peak blood level of 11-hydroxy-THC. Single dose; the authors recommended a longer study Side effects: Mild, transient side effects in 5 patients; no serious side effects. In the same trial's cognitive publication, no impairment in memory, reaction time or attention, but on a symptom scale (SCL-90-R) a trend toward worsening obsessive-compulsive behaviors and increased phobic anxiety | PMID 11951146, doi:10.1055/s-2002-25028, Cognitive safety publication of the same trial: Müller-Vahl 2001, PMID 11229617 |
| Eapen 2025 Open-label, single-arm pilot (feasibility) study (Australia, Sydney) | 10 (9 completed) Adolescents aged 12–18 with Tourette syndrome and a YGTSS tic score of at least 20 (mean age 14.4; of the 10, 6 had ADHD, 5 OCD, 9 anxiety, 4 autism); all had previously not benefited enough from medication, and 6 had also received behavioral treatment; those with a personal or family history of psychosis were excluded | Oral oil: 10 mg THC + 15 mg CBD per mL | Starting dose 1 mg THC/day; first step 5 mg THC/day under 50 kg and 10 mg THC/day at 50 kg and over; if no response, at most 10 or 20 mg THC/day Increased over 21 days (under 50 kg by 1 mg every 4–5 days, above that every 2–3 days); if no response on day 29, to the second step over 21 days; once a day, in the evening; split into two doses with side effects | 85 days (about 12 weeks) | The parent-rated tic scale (PTQ) fell from 69.8 to 40.1 on day 85 (p = 0.0038); the clinician-rated YGTSS score also fell (p = 0.0035); quality of life (parent and teen report) and behavioral-emotional problems (SDQ) improved; no significant difference in premonitory urge or ADHD symptoms. 7 of 10 teens did not respond adequately to the low dose. No comparison group and no blinding; no correction for multiple comparisons (two measures remained significant after Bonferroni correction) Side effects: No serious side effects; in reports outside the scale, most common were tiredness and sleepiness (40%), followed by dry mouth (30%); on the side effect scale, blurred vision, dry mouth, increased appetite and lack of motivation 22%; in 2 teens the dose was lowered to the lower step because of side effects | PMID 40636988, doi:10.1192/bjo.2025.35, ANZCTR ACTRN12622000031763. The manufacturer (Cann Group) supplied the drug free of charge, according to the article, the company had no role in the study, no private funding. The same team's placebo-controlled study: Efron 2025 |
| Anis 2022 Open-label, prospective, uncontrolled study (single center, Tel Aviv) | 18 (15 completed 12 weeks) Adults with Tourette syndrome (Israel; baseline YGTSS total 60.3 ± 17.1) | Medical cannabis: smoked or vaporized dried flower, or sublingual oil; initially 10% THC and 2% CBD | Mean 16.8 g/month (week 4) and 18 g/month (week 12); mean THC:CBD ratio at the end of the study 12.3:3.6 Started at 1 drop or 1 puff a day and increased one at a time as needed; adjusted by the patient | 12 weeks | Over 12 weeks, the YGTSS total score fell by an average of 38% (p = 0.002), the tic score by 35%, and the premonitory urge scale (PUTS) by 20% (p = 0.043); 93% of completers chose to use it by smoking or inhaling. No comparison group and no blinding Side effects: Dry mouth 67%, tiredness 53%, sleepiness and dizziness 47%; mental side effects in 6 of 15 people (sense of time, orientation, confusion, slowed thinking, attention); psychiatric side effects in 3 people: worsening OCD (stopped), panic attacks and anxiety | PMID 35310886, doi:10.1155/2022/5141773, NCT05115318, 18 people, 10% THC and 2% CBD, weeks 4 and 12, no registration number found in the article). The authors declare no conflicts of interest |
| Bloch 2021 Open-label, uncontrolled phase 2 pilot study (US, Yale University) | According to the registry, 17 started and 16 completed (the abstract says 16 people and 2 early dropouts; 12 moved into the 24-week extension) Adults with treatment-resistant Tourette syndrome (ages 18–56, mean 35) | THX-110: dronabinol (synthetic THC) + palmitoylethanolamide (PEA; a fatty acid amide also found in the body) | Dronabinol at most 10 mg/day + PEA 800 mg/day Dronabinol 2.5 mg for 3 days, 5 mg for 4 days, then 10 mg if tolerated; with side effects the dose was lowered, the increase slowed or the dose moved to the evening | 12 weeks (+ 24-week open extension) | The YGTSS total tic score fell by an average of 7.6 points over 12 weeks (95% CI 2.5–12.8; registry results), more than 20% on average according to the authors; improvement began in the first week. No comparison group; the authors stress that blinding is difficult because of THC's intoxicating effect. Sponsor: the university, with the company developing the drug (Neurothera Labs) as a collaborator Side effects: According to the registry, tiredness or sleepiness and feeling high in all 16 people; dry mouth in 15, dizziness and trouble concentrating in 13, anxiety and headache in 11, forgetfulness in 10, suspiciousness (paranoia) in 6, panic attacks in 4; no serious side effects; side effects were managed by lowering the dose, increasing it slowly and taking it in the evening | PMID 34340527, doi:10.1176/appi.neuropsych.19080178, NCT03066193, December 19, NCT03651726 |
| Wilson 2026 Systematic review and meta-analysis of RCTs (1980–May 13, 2025; PROSPERO CRD42023392718; GRADE) | 54 RCTs, 2,477 participants (all mental health conditions and substance use disorders; the number of tic studies is not in the abstract) People with a mental health condition or substance use disorder (including tic disorders and Tourette syndrome) | CBD, THC, THC and CBD combinations and other cannabinoids | In people with tics or Tourette syndrome, tic severity decreased compared with placebo (SMD −0.68; 95% CI −1.03 to −0.34); from the sentence in the abstract it is not clear whether this result applies only to THC and CBD combinations or to all cannabinoids, and the number of studies it is based on is not stated (the full text could not be read). The certainty of the evidence is low for most outcomes, and 44% of the studies have a high risk of bias. According to the authors, routine use of cannabinoids in mental health conditions can rarely be justified for now Side effects: People taking cannabinoids were more likely to have any side effect (OR 1.75; 95% CI 1.25–2.46; number needed to harm 7); no difference in serious side effects or study withdrawal | PMID 41856154, doi:10.1016/S2215-0366(26)00015-5, Correction: Lancet Psychiatry 2026, PMID 42302809, June 16, 2026: the axis of a figure and the study counts in the table were corrected, results unchanged). The same review is also in the tables of the anxiety, psychosis, depression, bipolar, sleep, substance use and autism topics | ||
| Bharat 2026 Systematic review and meta-analysis of experimental and observational studies (up to May 2025; PROSPERO CRD42023467536; GRADE) | 82 experimental and 118 observational studies (all diagnoses; the number of Tourette studies is not in the abstract) Adults (aged 18 and over) with ADHD, anxiety, depression, PTSD, psychosis, Tourette syndrome or substance use disorder | THC, CBD, combinations of the two and other cannabinoids; medical cannabis | In RCTs, cannabinoids had a negligible or no effect on Tourette syndrome (numerical result not in the abstract); small reduction in anxiety (SMD −0.40), no significant effect in depression. Observational studies suggest improvement, but the risk of bias is high. The certainty of the evidence is mostly very low; the authors do not support cannabinoids as a first-line treatment. The full text could not be read Side effects: The only significant safety finding: stopping because of side effects was more common with THC (OR 2.78; 95% CI 1.66–4.65) | PMID 42617303, doi:10.1016/j.psychres.2026.117380, The same review is also in the table of the Depression topic | ||
| Curtis 2009 (Cochrane) Cochrane systematic review (RCTs; CENTRAL 2008 issue 4, MEDLINE, EMBASE, PsycINFO and other databases) | 2 RCTs, 28 patients Patients with Gilles de la Tourette syndrome | THC (alone or added to another medicine) | The two studies found (one single-dose crossover, one 6-week parallel; 8 patients took part in both) reported a positive effect of THC, but the improvement in tic frequency and severity was small, was seen only on some measures, and many comparisons had been made; dropouts and withdrawals were high in the 6-week study. No quality-of-life data. According to the authors, there is not enough evidence to support the use of cannabinoids for tics and obsessive-compulsive behaviors. Not updated since 2009; it does not include the four later RCTs | PMID 19821373, doi:10.1002/14651858.CD006565.pub2, Previous version: CD006565 (protocol). PMC7387115 | ||
| Mann 2026 Systematic review and meta-analysis (PROSPERO CRD420251088633; up to July 2, 2025; cohorts and RCTs; before-and-after comparison) | 8 studies (7 in the meta-analysis), 306 adults Adults with Tourette syndrome | Cannabis-based medicines (various; most containing THC) | After treatment, the YGTSS score fell compared with before (mean difference −13.29; 95% CI −21.67 to −4.91; p = 0.002); premonitory urge scale (PUTS) −4.09 (−7.24 to −0.93; p = 0.01). The comparison is not against placebo but between the same people's scores before and after; this method cannot separate the placebo effect from tics easing on their own. The authors call for large placebo-controlled studies. The full text could not be read; which studies were pooled could not be verified | PMID 42229830, doi:10.1016/j.neuroscience.2026.05.044, Preprint: Europe PMC PPR911764 (2024) | ||
| Pringsheim 2019 (American Academy of Neurology) Systematic review (evidence review for the American Academy of Neurology tic treatment guideline; search August 2016, updated September 2017; RCTs with at least 20 people, or at least 10 in crossover designs) | 66 RCTs and 12 safety studies (all tic treatments); for THC, 2 RCTs (Müller-Vahl 2002 and 2003) Tourette syndrome and chronic tic disorders (children and adults) | All tic treatments; among cannabinoids, THC | 'Low confidence' was given that THC reduces tics more than placebo (SMD 0.62; 95% CI 0.01–1.22; two studies, one Class II and one Class III; adults only); pimozide, ziprasidone, metoclopramide, guanfacine and topiramate are at the same level. 'High confidence' for behavioral therapy for tics (CBIT); 'moderate confidence' for haloperidol, risperidone, aripiprazole, tiapride, clonidine and botulinum toxin. According to the same guideline's recommendation text (PMID 31061208), evidence is insufficient for nabiximols, nabilone, CBD and different cannabis strains; cannabis-based medicines may be considered in adults who have not improved with other treatments (Level C recommendation), the lowest effective dose should be used, and patients should be told they may affect driving; they should be avoided in children and adolescents because of the limited evidence and the possible harms of cannabis exposure in adolescence to thinking and mood in adulthood; they should not be used in pregnancy, breastfeeding or psychosis. Done before CANNA-TICS and Mosley 2023. One of the authors (Müller-Vahl) declares consulting fees, speaker fees and research support from cannabinoid companies | PMID 31061209, doi:10.1212/WNL.0000000000007467, Recommendation text of the guideline: Pringsheim 2019, PMID 31061208, PMC6537133). Correction: Neurology 2019, PMID 31451598, PMID 22397999, in adults only | ||
| Roessner 2022 (European Tourette guideline, ESSTS) Clinical guideline (European Society for the Study of Tourette Syndrome, 2nd version, pharmacological treatment section; literature search after 2011 and a preference survey of 50 experts) | Tourette syndrome and other tic disorders (children, adolescents and adults) | Cannabis-based medicines (cannabis flower, cannabis extracts, pure THC) | First choice is education and behavioral approaches; if medicine is needed, the most evidence is for dopamine blockers (preferably aripiprazole). Cannabis-based medicines are listed, together with pimozide, haloperidol, topiramate and botulinum toxin, among options that may be considered only in treatment-resistant cases. According to the guideline, no new RCTs had been published since 2011, and a meta-analysis pooling two small RCTs did not show a significant benefit of THC over placebo. Written before the CANNA-TICS results. One of the authors (the principal investigator of CANNA-TICS) declares consulting and research-support ties with cannabis companies | PMID 34757514, doi:10.1007/s00787-021-01899-z, PMID 34244849 | ||
| Treves 2025 National retrospective cohort (Israeli Medical Cannabis Agency prescription and dispensing data, April 2018–March 2022) | 1,341 children (165 with Tourette syndrome; ages 2–11) Children under 12 prescribed medical cannabis oil (autism, epilepsy, Tourette syndrome, cancer); adolescents and young adults for comparison | Cannabis oils with standard THC and CBD ratios, dispensed in Israel under a patient's medical cannabis permit. Of the 250 bottles given to children with Tourette syndrome at first dispensing, 176 (70%) were CBD-rich (most often 1% THC + 20% CBD; only 9 bottles were THC-free), 55 (22%) contained equal THC and CBD, and 19 (8%) contained more THC; in other words, 96% of the bottles contained THC (Supplementary Table S1) | Not reported (separately for Tourette syndrome) | First 3–6 months | In children under 12 with Tourette syndrome, fewer than 50% continued treatment through the first 3 months (from the figure); across all indications, about 60–70% of children stopped within the first 6 months, and for most, the THC ratio or amount was changed in the first months; the risk of stopping was lower in young adults than in children (HR 0.83; 95% CI 0.71–0.96). Effectiveness was not measured; reasons for stopping are given only in the open study of autistic children (mostly side effects and lack of benefit), with no separate reasons for Tourette syndrome | PMID 41357860, doi:10.3389/fphar.2025.1646560, PMC12678362, THC and CBD ratios of the first products dispensed are in Supplementary Table S1, dose and ratio changes in the first 6 months in Supplementary Figure S3 (Europe PMC supplementary file, October 28, 2026) |
| Barchel 2024 Prospective survey study from a patient registry (before treatment and after 6 months; no control group) | 70 registered patients; 57 answered the month-6 survey (3 aged 15–16) Patients with Tourette syndrome in a cannabis producer's (Tikun Olam) patient registry (Israel) | Licensed medical cannabis (THC and CBD) | Mean daily 123 mg THC and 50.5 mg CBD | 6 months | Among the 57 people who answered the survey at month 6, improvement in quality of life (p < 0.005), work status (p = 0.027) and number of medicines used (p < 0.005); motor tics (p = 0.375), vocal tics (p > 0.999), tic frequency (p = 0.062) and general mood (p = 0.129) did not improve significantly. Tics were asked about not with a scale but by patient report, as present/absent and daily/weekly. 67% of those with OCD and 89% of those with anxiety reported improvement. No control group. No funding; 1 of 7 authors is an employee of the cannabis company that owns the registry (Tikun Olam Cannbit) Side effects: Most common were dizziness (4 people) and increased appetite (3 people) | PMID 36342913, doi:10.1089/can.2022.0112, Israeli Ministry of Health registry 0185-19-ASF. PMC10874815 |
| Anis 2024 Retrospective long-term follow-up and structured survey (single center; no control group) | 25 Patients with treatment-resistant Tourette syndrome using licensed medical cannabis (Israel, Tel Aviv; 84% male) | Licensed medical cannabis; 96% mostly by smoking or vaporizing | Steady increase in monthly THC dose over the years (on average 0.6–0.7 g per year; p < 0.0001) Adjusted by the patient | Mean 4.0 ± 2.3 years (0.5–10 years) | Patients reported an average 75% reduction in tics and improvement in co-occurring symptoms (self-rated); according to the authors, the dose increases made by patients themselves suggest that tolerance may develop. No control group; only those who continued long-term use were studied Side effects: 88% reported at least one side effect (details not in the abstract) | PMID 37172308, doi:10.1089/can.2022.0281, From the same center (Movement Disorders Unit, Tel Aviv Sourasky Medical Center): the 12-week prospective study Anis 2022, whether patients in the two groups overlap is not stated |
| Milosev 2019 Retrospective chart review and online survey (single center; no control group) | 98 (chart review); 40 (online survey) Adults at the Tourette clinic in Hannover who had used cannabis-based medicines at any time (Germany) | Street marijuana (most common), nabiximols, dronabinol and prescription medical cannabis | According to Table 2 (prescription products), on average medical cannabis 2.2 g/day, dronabinol 43.2 mg/day, nabiximols 10.6 sprays/day; doses varied widely from person to person | Long term (duration varied by patient) | Of 38 patients able to compare, 66% preferred medical cannabis (THC-rich varieties), 18% dronabinol, 11% nabiximols and 5% street marijuana. According to patients' accounts, tics improved by about 60% in 85% of users, co-occurring problems improved in 55% and quality of life in 93%; the online survey pointed the same way. 31 of 98 patients (33%) stopped treatment (reasons unknown); in about half (51%) of the reports on prescription products, the effect had faded over time before the dose was adjusted. Retrospective and uncontrolled; only people who came to the clinic and used cannabis. 1 of 5 authors (the senior author) declares consulting fees, speaker fees and research support from cannabinoid companies Side effects: Side effects in half of patients; tolerable according to the authors | PMID 31872061, doi:10.1089/can.2018.0050, PMC6922065. The same center ran CANNA-TICS |
Reported side effects
- With the oil containing THC and CBD, slowed thinking, forgetfulness and trouble concentrating in 8 of 22 people; during the placebo period the most common side effect was headache (7 people) (Mosley 2023)
- With a single dose of inhaled marijuana, side effects were more common than with placebo for all products, most of all with the THC-rich product (cognitive and psychomotor effects) (Abi-Jaoude 2023)
- In teens: in the placebo-controlled pilot study the most common was dizziness (67%), no serious side effects (Efron 2025); in the uncontrolled study the most common were tiredness and sleepiness, followed by dry mouth; blurred vision, increased appetite and lack of motivation 22% (Eapen 2025)
- With THC combined with palmitoylethanolamide over 12 weeks: tiredness or sleepiness and feeling high in all 16 people, dry mouth in 15, trouble concentrating in 13, anxiety in 11, forgetfulness in 10, suspiciousness (paranoia) in 6, panic attacks in 4; no serious side effects (Bloch 2021, registry results)
- With medical cannabis (mostly smoked): dry mouth 67%, tiredness 53%, sleepiness and dizziness 47%; mental side effects in 6 of 15 people; worsening OCD, panic attacks or anxiety in 3 people (Anis 2022)
- 88% of people who used medical cannabis for years reported at least one side effect (Anis 2024)
- Across all mental health condition studies, the chance of side effects rose with any cannabinoid (OR 1.75; no difference in serious side effects; Wilson 2026); stopping because of side effects was more common with THC (OR 2.78; Bharat 2026)
- With the mouth spray containing THC and CBD over 13 weeks, any side effect 95.3%, with placebo 78.8%; most common were feeling strange (40.6% versus 3.0%), dizziness (35.9% versus 33.3%) and tiredness (29.7% versus 24.2%); palpitations 5/64 versus 0; stopping because of side effects 5/64 versus 1/33; a serious side effect in 1 person in each group (CANNA-TICS, EU clinical trials register results)
Monitoring done in studies
- In a person using a THC-containing product, thinking, attention, mood and obsessive-compulsive symptoms should be monitored with a doctor; these side effects were common in the studies
- In the study with teens, kidney function and electrolytes were checked at baseline, and liver tests and a urine drug screen were done at baseline and on day 85 (Eapen 2025)
- Planned study: a crossover study comparing THC (dronabinol) combined with palmitoylethanolamide against placebo in 164 adults (NCT05126888) is listed in the registry as 'not yet recruiting' as of October 2026 (planned start June 2026, completion February 2028)
Who should be careful
- The positive results in Tourette studies came from THC-containing products; they cannot be cited as evidence for the CBD oils sold in Turkey
- Children and adolescents: the American Academy of Neurology guideline recommends avoiding cannabis-based medicines because of the limited evidence and the possible harms of cannabis exposure in adolescence to thinking and mood in adulthood (Pringsheim 2019). With THC-containing products there are only two pilot studies of 10 people each, and long-term safety is unknown; an expert editorial points to the link between regular THC use in adolescence and the risk of psychosis, and says behavioral therapy should be offered first (Abi-Jaoude 2026, PMID 41556111)
- Personal or family history of psychosis: this was an exclusion criterion in the study with teens (Eapen 2025); the American Academy of Neurology guideline recommends not using cannabis-based medicines in people with psychosis (Pringsheim 2019); according to an expert editorial, psychotic symptoms were seen with THC in Tourette studies, though rarely (Abi-Jaoude 2026)
- Obsessive-compulsive symptoms and anxiety: worsening OCD, panic attacks and anxiety were reported with THC-containing medical cannabis (Anis 2022)
- With long-term use, the THC dose rose from year to year; tolerance may develop (Anis 2024)
- Anyone taking a medicine long term should talk to a doctor before starting; the studies on this page did not systematically assess interactions
- Pregnancy and breastfeeding: the American Academy of Neurology guideline recommends not using cannabis-based medicines during these periods (Pringsheim 2019)
Drug interactions
- The studies on this page did not systematically assess drug interactions; details are in the site's drug interactions section
- Most participants were taking other medicines for tics, ADHD or OCD: in the studies, the doses of these medicines were kept stable for at least 30 days beforehand (CANNA-TICS protocol) or had to be unchanged for the past 4 weeks (Eapen 2025)
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
- Most tics ease after adolescence, and first-line treatment is education plus behavioral therapy; you can discuss these options with your child psychiatrist or neurologist.
- Do not stop your tic, ADHD or OCD medicines on your own; there is no evidence that CBD can replace them.
- Remember that the positive results in research came from THC-containing products, which are not the same as CBD oils.
- In children and teens, THC-containing products call for extra caution because of their effects on thinking and attention and the risk of psychosis; tell your doctor if there is a personal or family history of psychosis.
- Check the product label and certificate of analysis to find out whether it contains THC; THC-containing products can affect driving.
Choose your age group, medicines and situation to prepare a short summary you can take to your doctor. Nothing you enter is sent anywhere.
Bottom line
CBD oil has not yet been tested in Tourette syndrome, so it is not known whether it helps tics. Small studies with THC-containing products saw fewer tics, but in the largest study the difference did not meet the main measure; side effects affecting thinking and attention were also common. The strongest evidence for tics belongs to behavioral therapy; talking with the doctor who follows you or your child before trying anything new is the safest path.
Frequently asked questions
Does CBD oil work for Tourette syndrome?
There are no studies yet that can answer this. Oral CBD oil has never been compared with placebo in Tourette syndrome. CBD-dominant vaporized marijuana was tested as a single dose given once in a 12-person study, and it made no clear difference to tics. The positive results in studies come from THC-containing products; so the evidence for CBD is insufficient.
Does cannabis or THC reduce tics?
It did in some small studies, but the results are not consistent. In a 22-person study, an oil containing THC and CBD lowered the tic score more than placebo; in the largest study, with 97 people, the share of people whose tics fell by at least a quarter was higher with a mouth spray containing THC and CBD (21.9% versus 9.1%), but the difference was not statistically significant. THC can cause slowed thinking, dizziness and sleepiness; the strength of evidence is weak.
Can a cannabis product be used for my child's tics?
In children and teens there are only two small pilot studies (ages 12–18, 10 people each); the placebo-controlled one was designed not to test effectiveness but to see whether such a study was feasible. Long-term safety is unknown; regular THC use in adolescence has been linked to a risk of psychosis, and the American Academy of Neurology guideline recommends avoiding cannabis-based medicines in children and adolescents. Most tics ease after adolescence; first-line treatment is education and behavioral therapy. The decision should be made together with the child psychiatrist or neurologist who follows your child.
Does it help the ADHD, OCD or anxiety that often comes with Tourette syndrome?
In Tourette studies these were examined only as additional measures, and always with THC-containing products. In 22 adults with severe Tourette syndrome, an oil containing THC and CBD was reported to possibly reduce anxiety and obsessive-compulsive symptoms; in the 97-person study there was a trend toward improvement in depression; in the uncontrolled study with teens, there was no significant difference in ADHD symptoms. Worsening obsessions and panic attacks were also reported with THC-containing medical cannabis. For anxiety, see the site's separate anxiety pages.
Does adding CBD to THC reduce side effects?
Because some researchers think so, most studies used THC and CBD together; but there is no evidence showing this consistently. In the study with an oil containing equal amounts of THC and CBD, slowed thinking, forgetfulness and trouble concentrating were still common; in the studies with teens, dizziness and tiredness were also common.
Can CBD oil be obtained with a prescription for Tourette syndrome in Turkey?
In Turkey, products derived from cannabis are regulated by the Kenevirden Elde Edilen Ürünlere Dair Yönetmelik (Regulation on Products Derived from Hemp) dated January 31, 2026. These products, including CBD, may be sold only in pharmacies. Those classed as medicines or health products are dispensed with a prescription; the regulation does not state a prescription requirement for supplement products and cosmetics with a THC content of at most 0.3%. As of October 2026, there is no approved (licensed) CBD medicine in Turkey. If you are considering using it, talk to your doctor first.
References
Show 19 references
- Müller-Vahl 2023 (CANNA-TICS). Multicenter, double-blind, placebo-controlled, parallel-group phase 3b RCT (2:1 randomization; Germany). PMID 36878177, doi:10.1016/j.psychres.2023.115135, NCT03087201, no results in the registry), EU clinical trials register EudraCT 2016-000564-42 (results posted on December 31, 2023: primary outcome, dropouts, PMID 33324255, PMID 33594741, PMID 38265476, PMID 36213751
- Mosley 2023. Double-blind, placebo-controlled, randomized crossover study (Australia). PMID 38320199, doi:10.1056/EVIDoa2300012, ANZCTR ACTRN12618000545268 (target 24, enrolled 22, first participant March 2019, last data April 2022, funding Wesley Medical Research Institute, collaborator Lambert Initiative)
- Abi-Jaoude 2023. Double-blind, placebo-controlled, randomized crossover pilot study; single dose of each product (Canada, Toronto). PMID 36040329, doi:10.1089/can.2022.0091, NCT03247244, Toronto, January 2018–January 2020, terminated: recruitment took long, no results in the registry)
- Efron 2025. Double-blind, placebo-controlled, randomized crossover phase 1/2 pilot (feasibility) study (Australia, Melbourne). PMID 40082070, doi:10.1089/can.2024.0188, NCT05184478, May 2022–January 2024, drug made by Cann Group, no results in the registry). The same team's uncontrolled study: Eapen 2025. Assessment: Abi-Jaoude 2026 editorial, PMID 41556111, the author led the Abi-Jaoude 2023 study in adults, no declared conflicts)
- Müller-Vahl 2003. Double-blind, placebo-controlled, parallel-group RCT (Germany, Hannover). PMID 12716250, doi:10.4088/jcp.v64n0417, Cognitive safety publication of the same trial: Müller-Vahl 2003, PMID 12589392
- Müller-Vahl 2002. Double-blind, placebo-controlled, randomized crossover single-dose study (Germany). PMID 11951146, doi:10.1055/s-2002-25028, Cognitive safety publication of the same trial: Müller-Vahl 2001, PMID 11229617
- Eapen 2025. Open-label, single-arm pilot (feasibility) study (Australia, Sydney). PMID 40636988, doi:10.1192/bjo.2025.35, ANZCTR ACTRN12622000031763. The manufacturer (Cann Group) supplied the drug free of charge, according to the article, the company had no role in the study, no private funding. The same team's placebo-controlled study: Efron 2025
- Anis 2022. Open-label, prospective, uncontrolled study (single center, Tel Aviv). PMID 35310886, doi:10.1155/2022/5141773, NCT05115318, 18 people, 10% THC and 2% CBD, weeks 4 and 12, no registration number found in the article). The authors declare no conflicts of interest
- Bloch 2021. Open-label, uncontrolled phase 2 pilot study (US, Yale University). PMID 34340527, doi:10.1176/appi.neuropsych.19080178, NCT03066193, December 19, NCT03651726
- Wilson 2026. Systematic review and meta-analysis of RCTs (1980–May 13, 2025; PROSPERO CRD42023392718; GRADE). PMID 41856154, doi:10.1016/S2215-0366(26)00015-5, Correction: Lancet Psychiatry 2026, PMID 42302809, June 16, 2026: the axis of a figure and the study counts in the table were corrected, results unchanged). The same review is also in the tables of the anxiety, psychosis, depression, bipolar, sleep, substance use and autism topics
- Bharat 2026. Systematic review and meta-analysis of experimental and observational studies (up to May 2025; PROSPERO CRD42023467536; GRADE). PMID 42617303, doi:10.1016/j.psychres.2026.117380, The same review is also in the table of the Depression topic
- Curtis 2009 (Cochrane). Cochrane systematic review (RCTs; CENTRAL 2008 issue 4, MEDLINE, EMBASE, PsycINFO and other databases). PMID 19821373, doi:10.1002/14651858.CD006565.pub2, Previous version: CD006565 (protocol). PMC7387115
- Mann 2026. Systematic review and meta-analysis (PROSPERO CRD420251088633; up to July 2, 2025; cohorts and RCTs; before-and-after comparison). PMID 42229830, doi:10.1016/j.neuroscience.2026.05.044, Preprint: Europe PMC PPR911764 (2024)
- Pringsheim 2019 (American Academy of Neurology). Systematic review (evidence review for the American Academy of Neurology tic treatment guideline; search August 2016, updated September 2017; RCTs with at least 20 people, or at least 10 in crossover designs). PMID 31061209, doi:10.1212/WNL.0000000000007467, Recommendation text of the guideline: Pringsheim 2019, PMID 31061208, PMC6537133). Correction: Neurology 2019, PMID 31451598, PMID 22397999, in adults only
- Roessner 2022 (European Tourette guideline, ESSTS). Clinical guideline (European Society for the Study of Tourette Syndrome, 2nd version, pharmacological treatment section; literature search after 2011 and a preference survey of 50 experts). PMID 34757514, doi:10.1007/s00787-021-01899-z, PMID 34244849
- Treves 2025. National retrospective cohort (Israeli Medical Cannabis Agency prescription and dispensing data, April 2018–March 2022). PMID 41357860, doi:10.3389/fphar.2025.1646560, PMC12678362, THC and CBD ratios of the first products dispensed are in Supplementary Table S1, dose and ratio changes in the first 6 months in Supplementary Figure S3 (Europe PMC supplementary file, October 28, 2026)
- Barchel 2024. Prospective survey study from a patient registry (before treatment and after 6 months; no control group). PMID 36342913, doi:10.1089/can.2022.0112, Israeli Ministry of Health registry 0185-19-ASF. PMC10874815
- Anis 2024. Retrospective long-term follow-up and structured survey (single center; no control group). PMID 37172308, doi:10.1089/can.2022.0281, From the same center (Movement Disorders Unit, Tel Aviv Sourasky Medical Center): the 12-week prospective study Anis 2022, whether patients in the two groups overlap is not stated
- Milosev 2019. Retrospective chart review and online survey (single center; no control group). PMID 31872061, doi:10.1089/can.2018.0050, PMC6922065. The same center ran CANNA-TICS
Points that could not be verified from the full text
- The full text of none of the six controlled studies could be read; the figures were taken from abstracts, the CANNA-TICS protocol and statistics paper, the CANNA-TICS results posted in the EU clinical trials register, ANZCTR and ClinicalTrials.gov records, and the tables of reviews.
- CANNA-TICS response threshold: in the protocol (2020) and in the statistics paper published while the study was running (2021), it was defined as at least a 30% reduction in tic score; the abstract of the results paper says at least 25%. According to the EU clinical trials register, the 25% threshold was set during a blinded data review before the groups were unblinded; why it was changed could not be verified, because the full text of the results paper could not be read. According to the results in the register, the difference was also not significant with the original 30% threshold.
- The tic scores of the placebo-controlled pilot study in teens (Efron 2025), the fact that one teen was rated 'much worse' during the oil period, and the information that no statistical test of effectiveness was done were taken only from an editorial (Abi-Jaoude 2026); the full text of the study could not be read.
- The full texts of the two 2026 meta-analyses (Wilson 2026, Bharat 2026) and of the 2026 meta-analysis specific to Tourette syndrome could not be read: how many studies and which products the tic result is based on could not be verified; Wilson 2026's correction in the journal was read on October 29, 2026: only the axis of one figure and the study counts in a table were corrected, and the results did not change.
- A study whose results were not published: an RCT planned with 60 adults comparing THC (dronabinol) combined with palmitoylethanolamide against placebo (NCT03651726; in the EU register EudraCT 2018-000014-38, 'ENTOURAGE'; sponsored by the company developing the drug, at two sites in Germany): the ClinicalTrials.gov record has not been updated since 2018 and its status is 'unknown'; in the EU register the study appears as terminated early on July 29, 2019, without stating how many people were enrolled or why it was stopped; no results or publication (October 2026).
- The THC-containing medicines used in Tourette studies (nabiximols, dronabinol) are not licensed in Turkey: the TİTCK (Turkish Medicines and Medical Devices Agency) List of Licensed Human Medicinal Products (October 16, 2026) contains no cannabinoid medicine. The active substance of the mouth spray containing THC and CBD is on the TİTCK Foreign Active Substance List (September 28, 2026) among medicines that require a red prescription (Turkey's controlled-drug prescription) and can be imported from abroad with the agency's written approval; dronabinol is not on this list. Whether the agency has approved importing these medicines for Tourette syndrome could not be verified in this search.
Research history
Here we record what changed on this page, when and why, with dates. The newest change is at the top.
The last sentence of the page's short summary was rewritten in a calmer, more guiding tone: instead of "Talk to your doctor before you start.", it now says whom you can talk with, and about what, if you are considering CBD. The conclusion and the strength of evidence did not change.
The correction to the Wilson 2026 meta-analysis published in the journal was read: only the axis of one figure and the study counts in a table were corrected; the results on this page did not change.
Related studies: Wilson 2026, published April 2026 (online March 16, 2026) (PMID 41856154, doi:10.1016/S2215-0366(26)00015-5, Correction: Lancet Psychiatry 2026, PMID 42302809, June 16, 2026: the axis of a figure and the study counts in the table were corrected, results unchanged). The same review is also in the tables of the anxiety, psychosis, depression, bipolar, sleep, substance use and autism topics)
October 2026 additional review: sources found for this page during searches for other topics were read and added to the page. The supplementary table of the study examining national data on children receiving medical cannabis oil in Israel (Treves 2025) was read: most of the products given to children with Tourette syndrome were CBD-rich, but 96% of the bottles also contained THC; the row's product type was corrected to 'Contains THC' (the same publication is classified that way on the Autism page too), and the wording in the pure CBD section was clarified. The status of THC-containing medicines in Turkey was verified from TİTCK (Turkish Medicines and Medical Devices Agency) lists: they are not licensed in Turkey; the active substance of the mouth spray containing THC and CBD is on the list of medicines that can be imported from abroad with the agency's written approval, and dronabinol is not on this list. The conclusion and strength of evidence did not change.
Older changes (1)
Page published. This first assessment reviewed 19 studies.