The cortisol, serotonin and oxytocin are associated with repetitive behavior in autism spectrum disorder

• ASD showed higher levels of cortisol AUC and serotonin, lower level of oxytocin.
• Cortisol, serotonin, oxytocin were significantly associated with total RBS-R score.
• Cortisol, serotonin and oxytocin were significantly associated with subscales scores.
• The occurrence of RBs in ASD may due to a variety of pathological factors.

Repetitive behaviors (RBs) are a core feature of autism spectrum disorders (ASD). They constitute a major barrier to learning and social adaptation. Research on potential causes of RBs is still at an early stage. However, promising new ideas and evidence are emerging from neurobiology. Instead of testing single neurotransmitter or hormone, the present study examined the associations of cortisol, serotonin, and oxytocin on subscales of repetitive behavior scales-revised (RBS-R). The results demonstrated that the individuals with ASD showed higher levels of cortisol areas under curve (cortisol AUC), higher levels of serotonin, and lower level of oxytocin compared with the typically developing (TD) individuals. For individuals with ASD, the levels of cortisol AUC, serotonin and oxytocin were all significantly associated with total scores measured by RBS-R. In addition, the cortisol AUC was positively associated with the stereotyped and restricted behavior subscales scores. The level of serotonin was positively associated with the stereotyped and self-injurious behavior subscales scores. The level of oxytocin was negatively associated with compulsive, sameness and restricted behavior subscales scores. Therefore, cortisol, serotonin and oxytocin may all be involved in the occurrence of RBs in ASD. The occurrence of RBs in ASD may due to a variety of pathological factors, not just one factor.