Oxytocin Effect in Adult Patients with Autism: An Updated Systematic Review and Meta-Analysis of Randomized Controlled Trials

Introduction: The efficacy of oxytocin in the treatment of autism spectrum disorder (ASD) has not been fully characterized. This systematic review and meta-analysis study evaluated randomized controlled trials (RCTs) on the treatment of intranasally administered oxytocin for autism. Methods: The study was conducted in accordance with the PRISMA statement. Two authors searched Scopus, PubMed/ Medline, Google Scholar, and Web of Science search engines and databases from inception through December 2020. Quality assessment was carried out by with the “ROB-2, Cochrane collaboration's tool”. The random-effects model was used for pooled analyses. I2 and Q tests were used to investigate study heterogeneity. The visual inspection of funnel plots along with Egger’s regression asymmetry test was used to assess the potential sources of publication bias. Results: Ten RCTs were selected for the systematic review. No study corroborated the efficacy of oxytocin for the treatment of anxiety and repetitive behavior. One out of 4 studies reported clinical improvement in severity, and 1 out of 6 studies indicated improvement in social function. Our metaanalyses findings suggest that oxytocin shows no significant efficacy in the treatment of anxiety (SMD: -0.168, SE= 0.112; 95% CI: -0.387, 0.050, p = 0.132), repetitive behavior (SMD: -0.078, SE= 0.155; 95% CI: -0.382, 0.225, p = 0.614), social function (SMD: -0.018, SE= 0.133; 95% CI: -0.279, 0.242, p = 0.891) and severity (SMD: -0.084, SE= 132; 95% CI: -0.343, 0.175, p = 0.524) of autism. No significant heterogeneity nor publication bias were observed between studies. Conclusion: Our findings failed to corroborate the efficacy of oxytocin in the treatment of ASD. Nonetheless, given the several limitations of our study, the results should be interpreted cautiously and stimulate future research on this timely topic.