A long-term observational study published this week in Pharmacology Biochemistry and Behavior found that purified cannabidiol (CBD) was well tolerated and associated with sustained improvements in children with severe autism spectrum disorder.
The study was conducted by researchers from Equipo de Neurodesarrollo INIZIO in Tucumán, Hospital General de Agudos J.M. Ramos Mejía in Buenos Aires, and the Department of Neurology at Hospital de Pediatría Prof. Dr. J.P. Garrahan in Buenos Aires.
Researchers evaluated purified CBD as an add-on therapy in children and adolescents ages 3 to 18 with autism spectrum disorder severity levels 2 or 3, intellectual disability and treatment-resistant behavioral symptoms. The study followed 20 children who were enrolled between January and December 2023, with 13 completing long-term follow-up through June 2025.
The average follow-up period was 27.6 months.
Researchers found that improvements reported by caregivers during an earlier three-month study were either maintained or further improved during long-term follow-up. Standardized behavioral scales showed modest but sustained improvements, particularly in irritability, social withdrawal and hyperactivity.
According to the study, mild and temporary adverse events reported during the short-term phase, mainly irritability or decreased appetite, did not recur during long-term follow-up. Researchers also reported that concomitant medications were reduced in 40% of patients.
The authors noted that pharmacological options for autism-related behavioral symptoms remain limited, with risperidone and aripiprazole the only drugs approved by the U.S. Food and Drug Administration for irritability in autism, both of which are associated with potential side effects such as weight gain and metabolic issues.
Researchers said CBD has drawn interest due to its potential anxiolytic, anti-inflammatory and neuromodulatory properties, as well as evidence suggesting the endocannabinoid system may be altered in people with autism.
The study used purified CBD rather than CBD-enriched cannabis formulations containing THC, with researchers saying this was done to avoid exposure to THC and its psychoactive effects in children.
“In this long-term follow-up of children with severe ASD treated with purified CBD, no significant differences were observed between the three-month and the 26-month evaluations, suggesting that the initial improvements were maintained over time,” the researchers concluded. “Among patients who completed the extended follow-up, purified CBD was well tolerated and associated with sustained improvement in several symptoms.”
