ClinicalTrials.gov record NCT06261502

Effect of CANnabidiol on Anxiety and GABAergic Function in Individuals With Fragile-X Syndrome

Record copied from ClinicalTrials.gov: Oct 10, 2026AI summaries generated: Sep 5, 2026

Effect of CANnabidiol on Anxiety and GABAergic Function in Individuals With Fragile-X Syndrome

StatusRecruitingThe study is currently enrolling participants. Only the study team can say whether a particular person can join.
Study typeInterventionalA study in which researchers assign participants to one or more interventions, such as a drug, procedure, device, behavioural programme or other approach, to measure their effects.
PhasePhase 2A study that tests whether a treatment has the intended effect and continues to check safety, usually in a larger group than phase 1.
Age7 years old to 40 years old
SexAll
LocationCanada
AI summaryWhat this study is about, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

This Phase 2 randomized, quadruple‑masked crossover trial tests oral cannabidiol (CBD) in people with Fragile‑X Syndrome. Each participant receives 12 weeks of CBD (5 mg/kg/day for two weeks, then 10 mg/kg/day) and 12 weeks of matched placebo separated by an 8‑week washout, with assessments at baseline, 12, 20, and 32 weeks. Caregivers complete behavior and anxiety questionnaires and participants undergo cognitive testing, transcranial magnetic stimulation (TMS) and brain spectroscopy.

What it is studying. The study tests whether giving oral CBD affects clinical measures (anxiety, disruptive behavior, and behavioral inhibition) and objective measures of brain inhibition and estimated GABA concentrations in people with Fragile‑X Syndrome.

What the researchers hope to learn. To define the therapeutic potential of the endocannabinoid (eCB) system for Fragile‑X Syndrome by measuring how oral CBD affects GABAergic (inhibitory) brain function and the severity of clinical symptoms such as anxiety and disruptive behavior.

What this study is about

The study's own summary, as published on ClinicalTrials.gov. Underlined terms have a short explanation.

This study focuses on the therapeutic relevance of the endocannabinoid (eCB) system for the treatment of Fragile-X syndrome (FXS), the primary hereditary cause of autism spectrum disorder (ASD). Most individuals with FXS have moderate to severe intellectual disability (ID), and caregivers are mainly concerned about aggressive behavior and anxiety problems. Since FXS individuals have a normal lifespan, the overall lifetime cost for the Canadian society of a single case is estimated at $1.2 to $4.7 millions reaching $18 billions for all FXS cases. There is no cure for FXS, as all clinical trials so far have been unsuccessful.FXS is caused by transcriptional silencing of the Fragile X mental retardation protein (FMR1) gene, making FXS a simple model to study ASD and ID pathophysiological mechanisms. Of those, neuronal hyperexcitability is largely recognized as a core deficit in FXS, and a critical therapeutic target for the disorder. Using transcranial magnetic stimulation (TMS) in FXS patients, our team provided the first direct evidence of Gamma-aminobutyric acid (GABA) receptor a (GABAa) dysfunctions in humans with this disorder and showed that this inhibitory deficit is linked with cortical hyperexcitability (PMID: 31748507). Concurrent lines of evidence suggest that stimulation of the endocannabinoid (eCB) system with the administration of Cannabidiol (CBD) could upregulate GABAergic function and correct inhibitory deficits presumed responsible for the neuropsychiatric phenotype of FXS. CBD has been shown to increase GABA concentration levels in the brains of healthy individuals, an effect that could help correct the hyperexcitability typically found in FXS. Thus, this trial aims to define the therapeutic potential of the eCB system for FXS, by measuring the impacts of oral CBD administration on the principal inhibitory neurotransmitter system of FXS patients, and the severity of the clinical phenotype.

Interventions being studied

Being studied in this trial does not mean the treatment or procedure is approved or available for this condition.

Drug
  • CBD Oral Solution
  • Placebo

Eligibility

The criteria exactly as listed on ClinicalTrials.gov. Only the study team can say whether they apply to you.

Inclusion criteria

  • Molecular diagnosis of FXS
  • Age 7 to 40 inclusively
  • Overall ABC-C score > 20
  • Taking up to 3 psychoactive drugs
  • No therapeutic change for the last 3 months

Exclusion criteria

  • Taking valproic acid
  • Taking clobazam
  • History of liver problems
  • aspartate aminotransferase (AST) or alanine transaminase (ALT), > 3 times the reference values
  • Bilirubin > 2 times the reference values
  • Absolute contraindication to the use of TMS and MRI (e.g. presence of metal in the body), will also be considered as an exclusion criterion.

Study description and what participation involves

The registry record has no detailed description beyond the summary above.

AI summaryWhat participation may involve, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

Participants take an oral cannabidiol (CBD) solution and a matching placebo in a randomized crossover: one 12-week CBD period and one 12-week placebo period separated by an 8-week washout. Dosing begins at 5 mg/kg/day for two weeks, then increases to 10 mg/kg/day. At baseline, 12, 20, and 32 weeks caregivers complete behavior questionnaires (ADAMS and ABC-C FX) and participants complete a cognitive test (NIH Toolbox Flanker). Participants also undergo brain testing at those visits: transcranial magnetic stimulation (TMS) measures and magnetic resonance spectroscopy (MRS) to estimate brain GABA levels; the registry record does not list other participant services.

How the study is structured. This is an interventional Phase 2 study with randomized crossover assignment and quadruple masking. Participants are randomly assigned to start with either 12 weeks of CBD oral solution or 12 weeks of matched placebo, then have an 8‑week washout, then switch to the other treatment for 12 weeks. Dosing begins at 5 mg/kg/day for two weeks, then increases to 10 mg/kg/day. Outcomes are measured at baseline, 12, 20, and 32 weeks and include caregiver questionnaires (ADAMS, ABC‑C FX), a cognitive inhibition task (NIH Toolbox Flanker), TMS measures of intracortical inhibition/facilitation, and estimation of brain GABA by magnetic resonance spectroscopy.

Questions you could ask

These questions are suggestions for a conversation with the study team or your own clinician, not advice.

  • Some participants receive a placebo. How is that decided, and what happens for placebo-group participants when the study ends?
  • The listed sites are in Canada. Is any of them reachable for me, and does the study help with travel?
  • Which of the eligibility criteria would need to be checked with tests before I could join?

More on fragile X syndrome

Clinical trials20 trials listed for fragile X syndromeEvery trial the registry lists for fragile X syndrome, with recruitment status, phase and sites, updated from ClinicalTrials.gov.See all trials →Research updatesWhat changed in fragile X syndrome researchLatest monthly update: September 2026. Includes: Multiple behavior challenges. New research summarized each month in plain language, with links to every source paper.Read the latest update →

Important dates

Study start
Sep 1, 2025
Primary completion
Jul 1, 2028 (estimated)
Study completion
Dec 1, 2028 (estimated)
Target enrollment
40 participants (estimated)
Last updated on registry
Aug 28, 2026
Data verified
Oct 10, 2026

Sponsor and research team

The lead sponsor funds and oversees the trial. A pharmaceutical or biotech company sponsor typically means the study is testing that company's drug or device; a hospital, university, or government agency usually indicates investigator-initiated or publicly funded research.

Lead sponsor
Université de Sherbrooke
Principal investigator
Francois Corbin, Full professor, Department of biochemistry
Université de Sherbrooke
Collaborators
  • Canadian Institutes of Health Research (CIHR)
  • Jazz Pharmaceuticals
  • Centre de recherche du Centre hospitalier universitaire de Sherbrooke

Central study contact

If you're interested in participating, the central contact can answer general questions about the study — including eligibility requirements and how to find a recruiting site near you. Actual eligibility is determined by the site's medical team.

Participating sites (1)

Terms used on this page · explanations by MedicalUpdates.ai

contraindication
A reason a particular test or treatment should not be used for a person, for example a metal implant that rules out an MRI scan.
MRI
A scan that uses magnets and radio waves, not X-rays, to make detailed pictures of the inside of the body. Some implants and metal objects mean a person cannot have one.
Inclusion Criteria
The conditions a person must meet to be considered for the study, for example a confirmed diagnosis, an age range or a test result.
Exclusion Criteria
The conditions that rule a person out even if they meet the inclusion criteria, for example other illnesses, certain medicines or pregnancy.

The study record on this page is reproduced from ClinicalTrials.gov, a database of the U.S. National Library of Medicine, where it was submitted by the study sponsor. MedicalUpdates.ai does not own this content, is not affiliated with or endorsed by ClinicalTrials.gov, NIH, or the U.S. Government, and does not verify the record. Plain-language notes, the glossary and the questions above are added by this site; text in the boxes marked "AI summary" was written by an AI model and may contain errors. Registry records change over time. Check the original record for the current version and discuss eligibility or participation with a qualified healthcare professional.

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