A new study has found a connection between low levels of the hormone vasopressin and the inability of autistic children to understand that other people’s thoughts and motivations can differ from their own.
Vasopressin is a small-protein hormone that is structurally similar to oxytocin. Like oxytocin, it plays a role in social behavior. The findings raise the possibility that treatment with vasopressin could help autistic children with low levels of this hormone.
“Autistic children who had the lowest vasopressin levels in their blood also had the greatest social impairment,” said the study’s senior author, Karen Parker, Ph.D., associate professor of psychiatry and behavioral sciences at Stanford University School of Medicine.
For the study, researchers observed a particular social trait known as “theory of mind:” the ability to understand that others have unique and different perspectives. Poor “theory of mind” makes it difficult for people with autism to empathize and form relationships with others.
A notable finding was that children without autism can have low vasopressin levels without displaying any social impairment, Parker added; in other words, autism is not explained by a vasopressin deficit alone.
First, the researchers verified that vasopressin levels in the blood accurately reflected vasopressin levels in the brain. They did this by measuring the hormone’s levels simultaneously in the blood and cerebrospinal fluid of 28 people who were having the fluid collected for medical reasons.
Next, the researchers recruited child participants, ages three to 12, for behavioral testing. Of the 159 children chosen for the study, 57 had autism, 47 did not have autism but had a sibling who did, and 55 were typically developing children with no autistic siblings.
All of the children completed standard psychiatric assessments of their neurocognitive abilities, social responsiveness, theory of mind, and ability to recognize others’ emotions, which is known as affect recognition. All children gave blood samples that were measured for vasopressin.
In all three groups, children had a wide range of vasopressin levels, with some children in each group having low, medium, and high levels. Healthy children had similar scores on theory of mind tests regardless of their blood vasopressin levels; however, in children with autism, low blood vasopressin was directly linked to low theory of mind ability.
Parker and her co-researcher, Antonio Hardan, M.D., professor of psychiatry and behavioral sciences, are now looking into whether vasopressin treatment improves social ability in children with autism. They want to find out whether the hormone is beneficial only for autistic children with low vasopressin levels or whether it might benefit all children with autism.
Their findings are published in the journal PLOS ONE.