The findings, presented at the BA festival of Science in York, which followed a long term study of behavioral changes in children, brace the theory that neural changes, which predispose a child to autism, occur while its brain is developing in the womb. It also supports the thought that autism is the result of an "extreme male brain".
Says lead researcher Simon Baron-Cohen: "We knew that fetal 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."
Baron-Cohen's team studied 235 children born in 1999. Before birth, the researchers were able to measure the level of testosterone they experienced in the womb because the mothers underwent amniocentesis (a procedure that involves sampling of the fluid around the fetus).
The children being eight years of age currently, the researchers gave their parents a questionnaire which queried about the level of autistic traits shown by the children - such as whether the child preferred to play alone and whether they were good at memorizing numerical patterns such as car number plates and phone numbers. Answers to these can indicate a numerical score called the autistic spectrum quotient or AQ.
The scientists note that though the children themselves were not autistic, the questions measured personality traits that were typically much more extreme in autistic children.
In addition, the kids were given 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 discovered that the level of testosterone in the womb was closely linked with both the children's performance in the test and their AQ.
According to them, the results are consistent with the notion that testosterone pushes brain development in a more autistic direction and that autism is the manifestation of an "extreme male brain".
"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," explains Prof Baron-Cohen. It is said that on average women tend to be better empathizers but men tend to be better systematisers — meaning they are better at understanding and manipulating mechanical objects.
In addition to this, previous tests of these kids at 12, 18 and 48 months old showed that those with higher fetal testosterone were less sociable.
Baron-Cohen's team is now studying 90,000 samples from Denmark's Biobank, in order to find out whether autism is really the result of an ultra-masculinised brain caused by high testosterone levels in the womb. The country has collected and preserved every amniocentesis sample produced since 1980, along with other tissues. Baron-Cohen's team plans to link these samples to a database of psychiatric diagnoses and examine the level of testosterone in every person diagnosed with autism.
Yet, even if it can be proved that testosterone is a causal factor in autism it may not be possible or even ethical to do anything about this. Previous studies suggest that the level is mostly down to the child's genes. Researchers currently, do not know which environmental factors are important.
"There is a very live debate about whether autism should simply be recognized as an atypical pattern of development like left handedness which doesn't necessarily need treatment," says Baron-Cohen, "It just needs to be recognized as different and maybe supported educationally but not cured or eradicated."