Scientists have discovered that monkeys with low levels of social behavior harbor low amounts of a hormone found in brain and spinal cord fluid. Although preliminary, they believe their findings suggest that the hormone arginine vasopressin (AVP) could be a target for developing drugs to alleviate social impairment in diseases such as autism spectrum disorder (ASD). ASD affects 1 in 68 children in the U.S. and incurs approximately $236 billion in annual expenses. However, the condition is difficult to directly study in patients, and mouse models fail to capture many of the complex social cognition aspects of the disorder. What's more, lab-based diagnostics and approved medications that detect and treat ASD do not exist. Karen Parker and colleagues developed a monkey model of low sociality that more accurately reflects certain aspects of social impairments in ASD patients. They studied the behavior of 42 male monkeys and identified low-social animals, which spent less time engaging in grooming and other social activities. Parker et al. then measured the concentrations of several molecules to spot any potential biological differences between low-social and high-social monkeys. Notably, the low-social monkeys had lower concentrations of AVP in the cerebrospinal fluid (or CSF), a discovery that was replicated in a separate group of monkeys. The authors also examined CSF samples from a group of seven children with ASD and found they had lower AVP concentrations compared to children without ASD. The researchers say further studies should aim to reproduce their preliminary findings in a much larger patient group, and assess whether CSF-AVP concentration also differs in adults with ASD.