CBD for autism

CBD is not a proven treatment for autism. A few small trials of CBD-rich cannabis extracts reported changes in some behaviour measures in autistic children and young people, but the products in the largest trial also contained THC. Trials of purified CBD on its own have been reported as showing no benefit.

What the research shows

The pooled trials in autism measured things like social responsiveness and disruptive behaviour.

Trials of CBD-rich extracts (contain THC)

The largest trial was run in Israel and published in 2021. It enrolled 150 autistic participants aged 5 to 21 and compared three groups: a whole-plant cannabis extract, purified cannabinoids and placebo. Both active products had a CBD to THC ratio of 20 to 1, so both contained THC. The authors described it as a proof-of-concept study.¹

A 2025 meta-analysis (a study that pools trials) combined 3 randomised trials with 276 participants. It found that CBD cannabis extracts improved social responsiveness, with a moderate to large effect size, and disruptive behaviour, with a small effect size.²

Three small trials are a thin base, and the largest used products with THC in them. THC is the compound in cannabis that causes a high, and it acts differently from CBD. See CBD vs THC.

Trials of CBD oil and purified CBD

• An Australian trial. Researchers ran a crossover trial of CBD oil in autistic children aged 5 to 12. In a crossover trial each child takes both the CBD and the placebo at different times. Twenty-nine children completed it.³ We have not been able to confirm its detailed results, and a trial this size can only detect large effects.
• Null results. A published commentary discusses recent randomised trials of purified CBD in autism that found no benefit over placebo.⁴

The pooled evidence across all cannabinoids

A 2026 review in The Lancet Psychiatry pooled trials of all cannabinoids, including THC-containing products, across mental and developmental conditions. It reported that cannabinoids reduced autistic traits, and rated that evidence as low certainty. Its overall conclusion was that routine use of cannabinoids for mental disorders “is currently rarely justified”.⁵

What this adds up to

There is a signal from CBD-rich extracts that contain a little THC, and reports of no benefit from purified CBD. That split is the reason for the “limited evidence” grade. It is possible the small amount of THC matters, and it is also possible that the positive results will not hold up in larger trials. See how we grade the evidence.

What doses were tested

The trials did not share one standard product or dose. The clearest point is the make-up of the products: the largest trial used a 20 to 1 ratio of CBD to THC, so participants on either active product also received THC.¹

No trial supports a particular dose of CBD for autism. For any prescribed product, the prescriber sets the dose.

What Australian medical bodies say

• Registered medicines. As of November 2026, only two cannabis medicines are registered in Australia. Epidyolex (CBD) is registered for seizures in two rare epilepsy syndromes (Lennox-Gastaut and Dravet syndromes), not for autism.⁶⁷
• RANZCP. The Royal Australian and New Zealand College of Psychiatrists says there is insufficient evidence to support medicinal cannabis as a treatment for mental disorders, and raises concern about overprescribing.⁸
• RACGP. The Royal Australian College of General Practitioners does not recommend or encourage the use of medicinal cannabis, and says it should only be considered after first-line, evidence-based treatments have been exhausted.⁹
• Youth mental health. A review of cannabinoids in young people concluded the evidence is “insufficient to broadly recommend cannabinoids” for mental disorders in this age group.¹⁰

See what Australian medical bodies say about CBD.

Risks to know about

• THC in children. The products in the largest trial contained THC.¹ Australian psychiatrists flag psychosis risk with high-potency THC products.⁸
• Side effects. In the epilepsy trials of prescription CBD, sleepiness or sedation affected 32% against 11% on placebo, and reduced appetite and diarrhoea were also more common.¹¹ See CBD side effects.
• Liver. In the epilepsy trials, liver enzymes rose to more than three times the normal upper limit in 13% of people on CBD against 1% on placebo. The rate was higher in those also taking valproate.¹¹ See CBD and the liver.
• Interactions. This matters most for a child who also takes medicines for epilepsy or another condition. CBD raises the active breakdown product of clobazam about three-fold and interacts with valproate.¹¹ See CBD drug interactions.
• Unregulated products. Products bought outside the prescription system may not match their labels, and some labelled as CBD contain THC.¹² The serious poisonings in children found in our research involved THC products, not pure CBD.¹³

Our page on CBD for children and teenagers covers these points in more depth.

If you are considering it

• Talk to your child’s paediatrician or psychiatrist first. Ask which supports and treatments have good evidence for the specific difficulty you want help with.
• Do not give a child any cannabis product that has not been prescribed for them.
• Questions worth asking: Does the product contain THC? What does the trial evidence show for my child’s age and needs? How would it interact with current medicines? What monitoring is needed? How will we judge whether it is working, and when would we stop?

This page is general information, not medical or legal advice. Laws and evidence change; we show the date we last checked the facts at the top of every page. Talk to your doctor or pharmacist before starting, stopping or changing any medicine.

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