Efficacy and Safety of Cannabinoid-Based Products in Children and Adolescents with Autism Spectrum Disorder, Fragile X Syndrome and Rett Syndrome: A Systematic Review

INTRODUCTION: Neurodevelopmental disorders (NDDs), including Autism Spectrum Disorder (ASD), Fragile X syndrome (FXS), and Rett Syndrome (RTT), share impairments in cognitive and behavioral functioning and may involve an altered excitatory/inhibitory balance modulated by the endocannabinoid system. This systematic review evaluated the safety and efficacy of cannabinoid-based products (CBPs) in these pediatric NDDs. METHODS: We conducted a systematic review according to Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) 2020, including randomized and nonrandomized studies of patients under 18 years treated with cannabidiol (CBD), cannabidivarin (CBDV), tetrahydrocannabinol (THC), or their combinations. Outcomes were adverse events (AEs) and treatment discontinuation, seizure reduction, and behavioral and cognitive changes. Study quality and certainty of evidence were assessed using design-specific risk-of-bias tools and the GRADE approach. RESULTS: Seventeen studies (two randomized controlled trials, observational studies, and case series) met the inclusion criteria. Across diagnoses, CBPs were generally associated with mild-to-moderate AEs and low discontinuation rates. Descriptive pooled proportions suggested behavioral improvements in ASD and FXS and seizure reduction in RTT, with exploratory analyses indicating differential effects of CBD versus CBD + THC on behavioral and cognitive outcomes in ASD. CONCLUSION: CBPs may offer potential benefits for selected behavioral symptoms and comorbid epilepsy in pediatric NDDs, but current evidence is insufficient to support routine clinical use. High-quality randomized controlled trials with standardized outcome measures and long-term follow-up are needed to clarify efficacy, safety, and syndrome-specific effects.