Vasopressin is a hormone for the heart in more ways than one. Not only does your brain pump it out when your blood pressure is low, it seems to play a role in falling in love. So it's no wonder researchers have turned to it in hopes of finding a treatment for those who struggle socially - and new results show they're on to something.
The good news is that two new clinical studies show vasopressin could help the social functioning of people on the autism spectrum ( ASD). The bad news? They don't agree how.
Groups of researchers from Stanford University and Roche independently trialled methods for modulating vasopressin – also known as anti-diuretic hormone – in participants with ASD.
Both groups reported some level of success in their respective trials. Unfortunately, while one team boosted the hormone in children, the other blocked its receptor in adults, leaving us with a paradox to solve.
Autism's characteristic traits can make it difficult for those diagnosed with the condition to form and maintain strong relationships. Not only are common interpersonal cues such as eye contact a problem, overwhelming responses to stimuli and challenges interpreting facial expression and language can interfere with social processes many of us take for granted.
Ever since vasopressin and its cousin oxytocin were found to play a role in complex social interactions in animals, researchers have wondered if they might be manipulated in humans in order to enhance our own relationships.
There are some fair reasons to think therapies based on these hormones might be of some benefit to those diagnosed with ASD, though the evidence has so far been somewhat circumstantial.
For example, in addition to its role in moderating blood pressure and social behaviours, vasopressin has been found to help mammals process sensory information.
In 2015, researchers found signs that vasopressin levels in the blood could be a useful biomarker for identifying which children with ASD readily relate to others.
Last year scientists found a concentration of vasopressin in the spinal fluid of children with ASD similar to depressed levels in the spinal fluid of monkeys with low levels of social interaction.
Evidence clearly leans towards the possibility of a vasopressin-based therapy for ASD, but transforming these hints into a physical product has proved easier said than done thanks in part to some seemingly contradictory experimental outcomes. For example, in voles higher levels of vasopressin raise aggression levels in males.
This inspired the Swiss pharmaceutical giant Roche to run clinical trials to investigate the blocking of vasopressin using an antagonist called balovaptan.
As a part of their ongoing Vasopressin Antagonist to Improve Social Communication in Autism (VANILLA) experiment, researchers recently posted the results of a 12 week long phase 2 trial on 223 men with moderate to severe ASD.
While standardised measures of social responsiveness fell short of being significant, those who received the largest doses of the vasopressin blocker showed improvements on other scales measuring social interactions, adaptive behaviours, and living skills.
Meanwhile, Stanford University researchers gave 17 children diagnosed with ASD a large dose of the hormone over a period of four weeks, and compared the effects with a placebo given to a separate group of 13 volunteers.
Based on their parents' responses, the children's general social responsiveness improved significantly. Other clinical assessments also showed an improvement in social communication scores, decreasing anxiety and even reducing some repetitive behaviours.
Taken together, these two outcomes don't make a great deal of sense. Vasopressin seems to make a difference both when elevated and when prevented from acting.
Reconciling these two very different approaches will no doubt demand a lot of extra research. Roche's results are a little less exciting by comparison, but the positive outcome still shouldn't be dismissed.
Putting aside the possibility that limitations in one or both experiments produced errors, the odd results could point the way to deeper complexities in how autism works in humans.
Vasopressin is clearly a multitasker – its role in our nervous system might not be as straight-forward as we assume. Among neurodiverse populations, its activity could be even more elusive, affecting different brains in different ways.
Overall, the research is a win for anybody hoping to see a hormone-based treatment that can help make socialising a little easier.
This research was published in Science Translational Medicine here and here.