BioEd Online

Hopes are growing that a hormone known to increase feelings of trust could also be used to treat autism.

The hormone oxytocin has been linked with various social behaviour traits in animals, including mother–infant bonding and sex. The hormone and neurotransmitter has also been shown to promote trust and other socially useful traits in humans¹.

Now evidence is building that oxytocin could be used to treat people with autistic spectrum disorders, which are often characterized by poor social interaction, repetitive behaviour and lack of communication. Currently there are no known cures or treatments specifically for autism.

In the most recent study, published in the Proceedings of the National Academy of Sciences, a French team investigated the effect of oxytocin on 13 adults with Asperger syndrome or high-functioning autism². Each adult was tested twice, once after being given either oxytocin or a placebo, in a randomized design, and again after being given the other treatment. The team's results are the first to show that administering the hormone can improve social behaviour.

"The effects in animals are strong. The effects in healthy volunteers are strong. The data that are accumulating now in patients with autism is also strong," says Eric Hollander, a research psychiatrist at the Montefiore Medical Center in New York who was not involved with the new research.

Pass the ball

Elissar Andari and Angela Sirigu, of the French national research centre (CNRS) in Bron, and their colleagues found that inhaled oxytocin increased the amount of time that patients could focus on the 'socially informative' regions of faces, such as the eyes. Failing to make eye contact is a trait of autistic disorders.

To investigate whether the treatment could actually improve behaviour, the team also got their participants to play a game that requires social awareness. The participants were asked to throw a virtual 'ball' to one of three simulated partners and receive the ball back. Over time, the researchers changed the behaviour of the partners so that eventually one would always throw the ball back to the human player — the good player — and one would never pass back.

After receiving a placebo the patients did not seem to be able to discriminate between the 'good' and 'bad' players. However, after inhaling oxytocin they sent many more balls to the 'good' player than to the player who never passed back.

"I think we show an efficacy that can be taken seriously," says Sirigu, director of the CNRS Centre for Cognitive Neuroscience in Bron. At the moment, she adds, "we have nothing for these patients".

"Oxytocin has potential," she adds. "We are sure in some patients it works."

Although it hasn't provided evidence of long-term benefit, Sirigu's work is one of a small number of papers that have excited the field of autism research. In 2007, Hollander published a study in Biological Psychiatry showing that the ability of adults to process and retain the emotional intonation in a sentence improved after administration of intravenous oxytocin³.

And last year, a team led by Adam Guastella, a senior researcher at the Brain and Mind Research Institute at the University of Sydney, Australia, showed that young patients with autism who received inhaled oxytocin performed better in a task involving recognizing emotions expressed in photographs of people's eyes than did those who received a placebo⁴.

"Oxytocin is the first medication to improve eye gaze and social cognition in autism, at least in the short term. This is incredibly exciting as we currently do not have effective interventions for social problems in autism," says Guastella. "The research is developing at a cautious pace but there is little doubt that within the next few years there will be multiple published randomized controlled trials of oxytocin to treat autism spectrum disorders."

Simon Baron-Cohen, director of the Autism Research Centre at the University of Cambridge, UK, says that the new study adds to the growing evidence that oxytocin is associated with enhanced social skills for people with and without autism spectrum conditions. But questions remain, he adds. "First, if oxytocin has a very short half-life — minutes rather than hours - how practical is this as a potential 'treatment'? Second, although oxytocin seems to enhance social skills, it is known to affect a number of other systems — including sexual arousal and lactation — so this may mean that some of its effects are unwanted."