Cannabidiol for behavioural symptoms in paediatric autism spectrum disorder: a systematic review

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by persistent deficits in social communication and interaction, alongside restricted, repetitive patterns of behaviour. In many cases, ASD is also associated with significant behavioural and emotional challenges, including irritability, aggression, hyperactivity, anxiety, sleep disturbances and stereotyped behaviours. These symptoms can substantially impair daily functioning and quality of life for both individuals and their families. Although pharmacological treatments such as antipsychotics may be effective in reducing severe behavioural dysregulation, their clinical utility is often constrained by adverse effects, including weight gain and sedation. Recently, cannabidiol (CBD) has gained attention as a potential alternative or adjunctive treatment due to its multimodal neurobiological actions, particularly involving endocannabinoid modulation and serotonergic signalling pathways. Nevertheless, current evidence regarding its efficacy and safety in paediatric ASD populations remains inconsistent and heterogeneous.

Aims: This study aimed to systematically evaluate the efficacy and safety of cannabidiol in managing behavioural symptoms in children and adolescents diagnosed with autism spectrum disorder.

Methods: A systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Electronic databases, including PubMed and LILACS, were searched using combinations of keywords related to autism spectrum disorder, cannabidiol and paediatric populations. Eligible studies comprised clinical trials and observational research investigating CBD-containing interventions in children and adolescents with ASD. Exclusion criteria included review articles, case reports, animal studies and opinion-based publications. Due to considerable heterogeneity across study designs, CBD formulations, outcome measures and follow-up durations, a meta-analysis was deemed inappropriate. Instead, findings were synthesized narratively.

Results: A total of 188 records were initially identified, with 116 remaining after removal of duplicates and screening. Fifteen studies met inclusion criteria, encompassing 1,124 participants, with sample sizes ranging from 20 to 188 individuals. The evidence base included three randomized placebo-controlled trials alongside several prospective and retrospective observational studies. Across the included studies, CBD use was associated with improvements in irritability, aggression, hyperactivity and anxiety. Approximately 60–70% of participants were reported to experience clinically meaningful benefits. Additional reported outcomes included enhanced social interaction, reductions in repetitive behaviours, improved sleep patterns and better overall family quality of life. One study reported improvement in at least one target symptom in up to 90% of participants, while another noted partial reduction or discontinuation of concurrent psychotropic medications in around 40% of cases. However, findings from placebo-controlled trials were mixed, with some demonstrating significant benefits and others reporting no meaningful changes in outcomes such as sleep or adaptive functioning.

Adverse events included somnolence, appetite changes, gastrointestinal disturbances, irritability and transient sleep disruption. Rare but notable severe neuropsychiatric effects, such as transient psychotic symptoms, were reported in isolated instances.

Conclusions: Cannabidiol appears to be a promising adjunctive intervention for behavioural dysregulation in paediatric ASD, particularly in reducing irritability, aggression and hyperactivity. However, current evidence is limited by methodological variability, short follow-up periods and reliance on caregiver-reported outcomes. Further large-scale, well-designed randomized controlled trials with standardized formulations and long-term safety assessments are necessary before CBD can be recommended for routine clinical use.

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