Plasmatic Levels of Neuropeptides, Including Oxytocin, in Children with Autism Spectrum Disorder, Correlate with the Disorder Severity

Context: Oxytocin has been investigated as a potential medication for psychiatric disorders. Objective and design: This study prospectively investigates correlations between oxytocin and other neuropeptides plasma levels in patients with autism spectrum disorders (ASD) according to severity and treatment, as compared to controls. Subjects and methods: Thirty-one children (6 neurotypical as control) participated in this study. The patients were classified into mildly and severely-affected, according to Autism Diagnostic Observation Schedule (ADOS) scores. Oxytocin, orexin A and B, α-MSH, β-endorphins, neurotensin and substance P were investigated using a quantitative multiplex assay or a competitive-ELISA method. Results: Plasma oxytocin levels differed between the groups (F (2, 24) =6.48, p=0.006, η2=0.35, observed power=86%): patients with the mild ASD had higher values of plasma oxytocin than those with the severe form (average difference=74.56±20.74pg/mL, p=0.004). Conclusions: These results show a negative correlation between plasma levels of oxytocin and the severity of ASD and support the involvement of oxytocinergic mechanisms in ASD.