British Association for the Advancement of Science festival:There is an increased risk of a child developing autistic traits if the child was exposed to raised levels of the male sex hormone testosterone while in the womb. This new finding represents the first time that an association has been established between hormone levels in the womb and autistic traits, according to the researchers.
Prof Simon Baron-Cohen and Dr Bonnie Auyeung of the University of Cambridge presented their important new work yesterday at the BA festival of science taking place in York. Prof Baron-Cohen stressed, however, that this did not confirm a link between foetal testosterone exposure and autism.
Autism was not part of the ongoing study which involved the measurement for testosterone in the amniotic fluid from 235 pregnancies. All of the children from these pregnancies were developing normally, he said. Some, however, have exhibited autistic traits as determined by questionnaires filled in by parents and by several developmental tests carried out with the children, who at this stage are eight years old.
The goal was to see if a "correlation" or association could be established between raised testosterone levels and autistic traits, Dr Baron-Cohen indicated.
He described autistic traits as behaviours linked to social development, for example whether the child preferred solitude to being social, with the former representing an autistic trait. Another is pattern recognition, for example an early ability to see numerical patterns, remember phone numbers or number plates, which again is an autistic trait.
Other signs of autistic traits by age 18 months include how often a child looks at faces or uses pointing gestures. These would be infrequent in a child with autistic traits.
The team has in fact established a correlation. "This study is new at showing the correlation between foetal testosterone and autistic traits," he said. "We don't know the causes of autism and are not sure whether the correlation found is part of a cause of autism or a byproduct or indication of an interaction."
The work was "novel" in that it looked at autistic trait distribution across a general population. "This is the first time that this has been related to foetal testosterone in the womb," Dr Baron-Cohen stated. He could not quantify the effect, as this information was part of a yet-to-be-published research paper.
Scientists are anxious to understand the causes of autism, which according to figures is on the increase, he said. Thirty years ago four cases per 10,000 children were diagnosed, but a Lancet study published in 2006 showed that one in 100 children were now diagnosed with autism.
Dr Baron-Cohen acknowledged that part of the increase was probably linked to better diagnosis and the inclusion of sub-groups of developmental disorders such as Asperger's syndrome.
Interest in foetal testosterone levels emerged after animal studies showed that higher levels were linked to alteration of brain development. Currently there is no evidence that testosterone levels were linked to brain development or autism in humans.
The study now makes a connection between the hormone and autistic traits. "All I can say is that foetal testosterone and autistic traits in this study correlate. We cannot infer a causal relationship," Dr Baron-Cohen cautioned.
His research sample was small but funding has been provided enabling the team to study 90,000 amniotic samples currently held in Denmark's Biobank. These samples date back to 1980 and are linked to any subsequent psychological diagnosis in the children involved.
"Therefore we will be able to test for a direct link between foetal testosterone and autism," Dr Baron-Cohen stated.