A single 600 mg dose of CBD increased brain activity in the cerebellum and fusiform gyrus, effects primarily driven by the autism group. CBD also altered connectivity between the cerebellum and striatum in participants with ASD only.
Autism researchers, CBD scientists, and families considering CBD for ASD.
CBD altered brain activity in ASD participants but not controls
What the researchers found
CBD significantly increased fractional amplitude of low-frequency fluctuations (fALFF) in the cerebellar vermis and right fusiform gyrus across all participants, but post-hoc analysis showed this was driven by the ASD group with no significant change in controls. In ASD participants only, CBD altered functional connectivity between the cerebellar vermis and subcortical/cortical targets.
Why it matters
This is one of the first studies to directly measure how CBD affects brain activity in people with ASD. The finding that CBD had a different effect in ASD versus controls suggests it may preferentially target neural circuits that are already atypical.
The numbers in context
34 men (17 ASD, 17 controls). 600 mg CBD or placebo. CBD increased fALFF in cerebellar vermis and right fusiform gyrus (primarily in ASD). CBD altered vermal functional connectivity in ASD only.
How the study worked
Double-blind, placebo-controlled, crossover design. 34 healthy men (17 with ASD, 17 neurotypical controls) received 600 mg oral CBD or placebo. Task-free fMRI was acquired to measure brain activity and functional connectivity.
What this study cannot tell us
Small sample size. Single dose only. All male participants, limiting generalizability. The study measured brain activity changes, not behavioral outcomes.
How to read the evidence
Moderate: randomized, double-blind, placebo-controlled crossover design, but small sample and single dose.
When this study was published
Published in 2019.
The bigger picture
The cerebellar vermis and fusiform gyrus are both regions consistently implicated in ASD. Finding that CBD selectively modulates these areas in people with autism provides a neurobiological rationale for further clinical trials.
Questions still open
- Do these brain changes translate to behavioral improvements? Would repeated dosing produce different or stronger effects? Would women with ASD show the same response?
Common questions
Does this prove CBD helps autism?
Why did CBD affect ASD brains differently than typical brains?
Read the original research
The effect of cannabidiol (CBD) on low-frequency activity and functional connectivity in the brain of adults with and without autism spectrum disorder (ASD).
Journal of psychopharmacology (Oxford, England), 33(9), 1141-1148
Citation
Pretzsch, Charlotte M; Voinescu, Bogdan; Mendez, Maria A; Wichers, Robert; Ajram, Laura; Ivin, Glynis; Heasman, Martin; Williams, Steven; Murphy, Declan Gm; Daly, Eileen; McAlonan, Gráinne M. (2019). The effect of cannabidiol (CBD) on low-frequency activity and functional connectivity in the brain of adults with and without autism spectrum disorder (ASD).. Journal of psychopharmacology (Oxford, England), 33(9), 1141-1148. https://doi.org/10.1177/0269881119858306
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