The relationship between cannabis and autism has only been studied for a few years and the scientific evidence is still limited. Some small trials suggest that certain CBD-rich extracts could improve behavioural problems associated with autism spectrum disorder (ASD), but the results are mixed and no cannabinoid medicine is authorised for autism. In this article we review what is known, what the most recent scientific reviews say and what is legal in Spain for families.
Notice: this article is for information only and is not a substitute for medical advice. Always consult your doctor before using cannabis or CBD.
Short answer: cannabis does not cure autism. Some studies with CBD-rich extracts have observed improvements in disruptive behaviour or irritability in children and young people with ASD, but they are few, small and their results are inconsistent. Its use should only be considered with a specialist and through legal channels.
Quick summary
Does cannabis work for autism? The evidence is limited. There are promising signals for some symptoms, but not enough proof to recommend it in general.
What do the reviews say? A 2024 systematic review found a small to moderate benefit and called for larger trials before recommending it.
Does it have side effects? Yes. The most common in trials were drowsiness and loss of appetite. In addition, THC can affect the developing brain.
Is it legal in Spain? No cannabinoid medicine is authorised for autism. CBD oils for ingestion are not authorised as food.
What is autism?
The word autism usually refers to autism spectrum disorders (ASD). These are neurodevelopmental disorders that show mainly as difficulties in communication and social interaction, and as restricted and repetitive patterns of behaviour, interests or activities. Many people with ASD are also especially sensitive to stimuli such as noise or light.
ASD varies greatly: no two people experience it in the same way. Its causes are not fully established, although it is known to have a significant genetic component and to appear in the first years of life. It is not a disease that can be “cured”: support and therapies aim to improve communication, independence and quality of life, and in some cases to treat associated problems such as irritability, anxiety, sleep disorders or epilepsy.
Cannabis and autism: how could cannabis act in ASD?
The hypothesis behind the research is based on the endocannabinoid system, a set of receptors and substances produced by the body itself, such as anandamide, which helps regulate emotions, sleep and social behaviour. Plant cannabinoids, such as CBD and THC, act on this system and can influence neurotransmitters such as serotonin and dopamine.
Some studies have observed differences in this system in people with ASD. In a study in mice published in 2015, anandamide signalling was found to be necessary for the effect of oxytocin, a hormone linked to social reward. These are interesting laboratory findings, but they do not show that taking cannabis improves social interaction in a person with autism.
What clinical studies say about cannabis and autism
The Shaare Zedek trial in Jerusalem
The most cited controlled study was carried out at the Shaare Zedek Medical Center in Jerusalem, led by paediatric neurologist Adi Aran, and published in 2021 in Molecular Autism. It involved 150 people with ASD aged 5 to 21, who received for 12 weeks a whole-plant extract with a ratio of 20 parts CBD to 1 part THC, a purified mixture of CBD and THC in the same ratio, or placebo, and then switched groups.
- On one of the two main measures, a questionnaire on behaviour at home, there was no difference compared with placebo.
- On the other, the clinical rating of disruptive behaviour, 49% of those taking the whole-plant extract improved substantially, compared with 21% on placebo.
- The most common side effects were drowsiness and loss of appetite, and there were no serious treatment-related adverse events.
The authors themselves described the evidence of efficacy as mixed and insufficient and called for further trials. In other words, it is a promising result, not proof that cannabis works for autism.
What systematic reviews conclude
A systematic review of randomised trials published in 2024 in Child and Adolescent Psychiatry and Mental Health (Köck et al.) analysed cannabinoids in psychiatric disorders in children and adolescents. It found a small to moderate overall benefit, with the most consistent results in ASD, but considered the evidence too limited to recommend them in general and called for larger, controlled trials with comparable outcome measures.
Individual cases and testimonies
Before controlled trials existed, some cases received wide media coverage, such as that of Kalel Santiago in Puerto Rico, a boy who, according to what his doctor told Forbes magazine in 2015, spoke his first words after starting to take CBD oil. These testimonies help explain why many families are interested in cannabis, but they cannot tell us whether a treatment works: that requires trials with a control group and many more patients.
Risks of cannabis in children and adolescents with ASD
The use of cannabinoids in minors calls for particular caution. THC can affect the developing brain and cause effects such as anxiety, sedation or behavioural changes. CBD can interact with other medicines, such as some anti-epileptic drugs, and the product information for Epidyolex warns of possible increases in liver enzymes. Over-the-counter CBD oils, moreover, do not guarantee the dose or the absence of THC. This is why any decision should be made with the paediatric neurologist or psychiatrist who follows the person.
What is legal in Spain for families?
- Authorised medicines: Epidyolex, a CBD medicine, is authorised in the European Union for seizures associated with Lennox-Gastaut syndrome, Dravet syndrome and tuberous sclerosis complex, from the age of 2. Sativex is authorised for spasticity in multiple sclerosis. Neither is indicated for autism, although Epidyolex can be prescribed to a person with ASD who also has one of those epilepsies.
- Standardised cannabis preparations: Royal Decree 903/2025 allows hospital specialists to prescribe magistral formulas with standardised cannabis preparations, dispensed by the hospital pharmacy, when there are no authorised medicines or these have not worked. The indications are set out in the monographs of the National Formulary, and the preamble lists as those with the most evidence spasticity due to multiple sclerosis, severe refractory epilepsy, chemotherapy-induced nausea and refractory chronic pain. Autism is not among them. We explain this in our guide to medicinal cannabis regulation in Spain.
- Over-the-counter CBD oils: CBD cosmetics are legal if they comply with their regulations, but CBD oils and foods for ingestion are not authorised as novel foods in the European Union. More information in whether CBD is legal in Spain.
- Advertising: Royal Decree 1907/1996 prohibits advertising products that are not medicines by claiming they can prevent, treat or cure diseases. A CBD oil advertised “for autism” breaks the law.
Frequently asked questions about cannabis and autism
Does CBD cure autism?
No. Autism is not a disease that is cured with a medicine. Some studies suggest that CBD could help with symptoms such as disruptive behaviour, but the evidence is limited.
Is any cannabis medicine approved for autism?
No. Neither the European Medicines Agency nor the Spanish AEMPS has authorised any cannabinoid medicine for ASD.
What side effects does cannabis have in children with autism?
In trials, the most common were drowsiness and loss of appetite. THC can affect the developing brain and CBD can interact with other medicines.
Can a doctor in Spain prescribe cannabis to my child with autism?
Autism is not among the indications with the most evidence listed in Royal Decree 903/2025, and no cannabinoid medicines are authorised for ASD. If your child also has epilepsy such as Dravet or Lennox-Gastaut syndrome, their neurologist may consider Epidyolex.
Is it legal to give CBD oil to a child?
CBD oils for ingestion are not authorised as food in the European Union, and those sold as cosmetics are for external use. Do not give CBD to a minor without consulting their doctor.
You may also be interested in: CBD and cancer treatment: what the research says · How does medical cannabis help women? · Medical cannabis legalisation: uses and legal status in Spain and Europe
Do you need legal advice?
At S&F Abogados we have specialised in cannabis and CBD law for 14 years. We advise patients, families, professionals and companies on access to medicinal cannabis, the requirements for CBD products and health advertising. Find out about our medicinal cannabis licensing service, send us your query online or call us on 919 532 802.
