Salivary Oxytocin Levels in Young Children with Autism Spectrum Disorders (ASD) Compared to Healthy Controls

Background: Evidences from literature in oxytocin, imply possible beneficial effect of oxytocin administration on social and communicative dysfunctions seen in ASD and their neural underpinnings. The lower levels of plasma oxytocin in ASD have been demonstrated in few studies in children and adolescents with ASD in comparison with typically developing children. Studies investigating salivary oxytocin levels in children with ASD have shown that oxytocin is lower in ASD than typically developing controls, rise in salivary oxytocin levels after social interaction and elevation of oxytocin levels in the saliva after intranasal administration thus influencing social cognition.

Objectives: This study attempted to 1) investigate the levels of oxytocin in the salivary samples of young children with ASD and compared with healthy controls and 2) the correlation of oxytocin levels to symptom severity scores measured by Childhood Autism Rating Scale (CARS).

Methods: 24 children diagnosed with ASD (mean age-4.6 years) and 18 age matched controls were recruited for the study. CARS was applied and severity scores were calculated for each subject with ASD. Saliva samples were collected using chewable cotton rolls. Samples were stored at -80 degree Celsius until further assay. Oxytocin levels were estimated by ELISA using commercial kits.

Results: Children with ASD had a mean salivary oxytocin level of 47.9706 µIU/mL. The mean oxytocin levels in the controls were 29.5866 µIU/mL. Between cases and control, cases had significantly higher oxytocin levels in the saliva – p<0.009. There was no significant correlation between symptom severity measures by CARS scores (Mean – 38.1) and oxytocin levels of children with ASD.

Conclusions: This study showed that children with ASD had higher levels of oxytocin compared to controls. There was no significant correlation between symptom severity and oxytocin levels. While most studies have shown lower levels of plasma and salivary oxytocin in children with ASD, few studies have shown no differences between the groups. However, this study showed higher levels of oxytocin in the ASD group which is unusual. Some notable differences from past studies are that, this study included 3 to 5 years old children with low functioning ASD. ELISA was done using the direct assay method. Saliva was not lyophilized during storage. Significant differences exist between values observed in similar populations and are likely due to methodological differences, ethnic variability, socio-economic differences; thus making comparison between studies difficult. In conclusion, use of saliva sample for oxytocin estimation in ASD and its role as a robust marker is debatable. Further studies to replicate and/or validate findings in similar samples are needed, in order to draw translatable evidence.