Early and accurate diagnosis of autism is challenging because of the paucity of biomarkers for the disorder. The neurological systems involved in social interaction — the impairment of which is a hallmark of autism spectrum disorders — offer a promising line of investigation for new biomarkers. Karen Parker and colleagues at Stanford University are undertaking the first comprehensive study to examine the relationship between oxytocin biology, one such candidate biomarker, and social impairments in individuals with autism.
Oxytocin is crucial to maternal behavior, bonding, trust and other social behaviors. Animal studies have shown that interfering with the function of oxytocin or its receptor impairs social functioning. In the clinic, preliminary research has revealed that boys with autism have lower oxytocin levels than do typically developing boys, and certain variations in the gene for the oxytocin receptor have been linked to a greater risk of autism.
The researchers are examining oxytocin levels and variants in the oxytocin receptor gene in children who have autism, their unaffected siblings, and unrelated typically developing control children. Social functioning among the children is assessed using established diagnostic and phenotypic tests. A key feature of this pilot project is the inclusion of girls and unaffected siblings, two groups that are often excluded from autism studies, but which are essential to a broader understanding of the various manifestations of autism.
Preliminary results show that the oxytocin receptor gene affects multiple aspects of social functioning relevant to autism. Ongoing research includes examining whether these and other genetic findings are replicable in larger study populations (e.g., Simons Simplex Collection).
In the largest study sample evaluated to date, plasma oxytocin levels did NOT differ between affected children, their siblings, and age-matched controls, nor were plasma oxytocin levels related to social functioning. Ongoing research includes testing whether plasma oxytocin levels of study participants are associated with distinct social phenotypes (the identification of which is being made by cluster analysis). Because there is evidence suggesting that central and peripheral oxytocin systems may be functionally independent, Parker and colleagues also plan in future studies to examine oxytocin levels in the cerebrospinal fluid of children with autism.
Parker and colleagues believe that shedding light on the role of oxytocin in social functioning may lead to the discovery of biomarkers for autism, implementation of earlier and more accurate diagnostic methods, and development of the first therapeutic treatments for the social deficits seen in autism spectrum disorders.