Oxytocin: The Book
The Mother/Baby Attachment Gap

Oxytocin, Vasopressin and Autism

Sue Carter, one of the world's top oxytocin researchers, published a new paper examining the link between oxytocin, vasopressin and autism. The paper, "Sex differences in oxytocin and vasopressin: Implications for autism spectrum disorders?," reviews the scientific literature

There are two reasons why many researchers are looking for a connection between oxytocin and autism. First, five times as many boys as girls are diagnosed with autism, and oxytocin is normally more abundant in women's bodies. Second, most of the behaviors people with autism spectrum disorder aren’t so good at are the very behaviors that oxytocin influences: picking up social cues, affection, making friends, giving and receiving physical affection.

Carter is head of the University of Illinois' Brain Body Center, and the researcher who demonstrated the link between oxytocin and bonding. She was able to switch monogamous behavior on and off by blocking oxytocin in monogamous prairie voles or injecting it into the brains of promiscuous montane voles.

She looked at not only oxytocin but also vasopressin, a related neurochemical that's less understood. While estrogen increases the effects of oxytocin, vasopressin is androgen-dependent, and males have more receptors for it in the paraventricular nucleus, a part of the brain involved in coping with stress. In animals, vasopressin influences male behaviors including reacting to challenges, protecting the nest and offspring and some parenting activities. (The assumption is that mechanisms are similar in humans.)

One hypothesis is that there are optimal vasopressin levels needed for protection against ASD. Males might be more sensitive to stress while their brains and nervous systems are under development, both in the womb and after birth. Disrupting their neurochemical balance may make them more vulnerable to ASD.

Another hypothesis is that the oxytocin-enriched female nervous system has better protection against whatever stressors cause ASD.

Carter's review of the literature found support for the connection between disruption of the vasopressin system and autism.

One interesting idea Carter floats at the end is that female coping mechanisms may keep ASD-like behaviors from becoming full-blown. She writes, "Sexually dimorphic differences in coping mechanisms, including the willingness to use social interactions to down-regulate anxiety, could be another mechanism through which males and females might differ in the expression of the features of ASD. Knowledge of natural ways to stimulate the release of endogenous oxytocin or to inhibit 'excess' vasopressin might be protective."

In other words, females naturally seek support and comfort from others (a behavior psychologist Shelley Taylor dubbed "tend and befriend" in her book, "The Tending Instinct"). Women are better at giving themselves a natural oxytocin boost, and this ability may form while they’re young enough to compensate for autistic tendencies.