The holy grail of autism research is a reliable test for the condition – and researchers at the California National Primate Research Center (CNPRC), working with colleagues at the Stanford University School of Medicine, have made a promising discovery that may lead to just such a test.

According to the research team, reduced levels of vasopressin – a hormone found in the spinal fluid – may be connected to a reduction in socially acceptable behavior.

“What we consider this to be at this point is a biomarker for low sociability,” said John P. Capitanio, a CNPRC scientist and leader of the Neuroscience and Behavior Unit at the University of California-Davis.

Currently, medical professionals diagnose autism by looking for certain social behaviors. Unfortunately, these tell-tale signs often don’t appear until a child reaches age four or five, limiting opportunities for early treatments that can stem the condition’s progress.

“Right now, the diagnosis is based on parents’ reports of their children’s symptoms, and on clinicians observing children in the clinic,” said Karen Parker, associate professor of psychiatry and behavioral sciences at Stanford and the lead author of the new study.

Researchers looked for autism biomarkers in rhesus macaques, a species whose social capabilities are close to those of humans. The scientists measured levels of two hormones, oxytocin and vasopressin, in their blood and in their cerebrospinal fluid, which bathes the brain.

Monkeys in the less social group had significantly less vasopressin in their cerebrospinal fluid than nonhuman primates in the more social group. In particular, the levels accurately predicted the frequency with which individuals participated in social grooming, an important social activity for this species. Importantly, the team was able to replicate their finding that low vasopressin levels are associated with lower social functioning using a second, independent cohort of monkeys.

The researchers also compared vasopressin levels in seven boys with autism and seven others without the condition. Similar to the results with the rhesus macaques, children with autism had lower vasopressin levels than children without autism.

Moving forward, the researchers plan to test a larger group of nonhuman primates to determine whether the low hormone level can be detected before symptoms of impaired social ability emerge.

Reviewed August 2019

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Photo credit: Kathy West for the California National Primate Research Center