By: Douglas Mason - Assistant Editor
Posted 9/12/07 - Autism-like behaviour in children is linked to the amount of testosterone they receive whilst in their mother's womb, according to a long-term study of behavioural changes in children.
The research provides support for the theory that neural changes predisposing a child to autism happen while its brain is developing in the womb and that autism is the result of an "extreme male brain".
"We knew that foetal testosterone was correlated with so-called social development at earlier points in childhood, but we hadn't been able to look at so-called autistic traits before," said Simon Baron-Cohen at Cambridge University.
His team has been studying 235 children born in 1999. Before birth the researchers were able to measure the level of testosterone the children experienced in the womb because the mothers underwent amniocentesis - a procedure that involves doctors taking a sample of the fluid around the foetus - for other medical reasons.
Now that the children are eight, the researchers gave their parents a questionnaire which asked about the level of autistic traits shown by the children - whether the child prefers to play alone and whether they are good at memorising numerical patterns such as car number plates and phone numbers. This gives a numerical score called the autistic spectrum quotient, or AQ. The children are not autistic, but the questions measured personality traits that are more extreme in autistic children.
The team also gave the children a computer test which involved them finding a hidden figure embedded in an image on the screen. Autistic children typically do very well at this test. The team found that the level of testosterone in the womb was closely linked with both the children's performance in the test and their AQ.
The results are consistent with the idea that testosterone pushes brain development in a more autistic direction and that autism is the manifestation of an "extreme male brain". On average women tend to be better empathisers but men tend to be better systematisers.
"Children with autism seem to have a very strong exaggeration of the male profile because they have very strong interests in systems like numbers but have difficulties with empathy," said Prof Baron-Cohen.
The team is now studying 90,000 samples from Denmark's Biobank - the country has collected and preserved every amniocentesis sample produced since 1980, along with other tissues. Prof Baron-Cohen's team plans to link these samples to a database of psychiatric diagnoses. If it does turn out ultimately that testosterone is a causal factor in autism it may not be possible or even ethical to do anything to change it. Previous studies suggest that the level is mostly down to the child's genes. Researchers don't know which environmental factors are important.
"There is a very live debate about whether autism should simply be recognised as an atypical pattern of development like left-handedness which doesn't necessarily need treatment," said Prof Baron-Cohen. "It just needs to be recognised as different and maybe supported educationally but not cured or eradicated."