Autism linked to higher testosterone levels in the womb

14 September, 2007

There has emerged strong evidence that may soon lead scientists to discover the causes of autism, a brain disorder.

In the United Kingdom alone, autism, in one form or the other, today affects about one in every 100 children.

Scientists have found that raised levels of the sex hormone testosterone in the womb of pregnant women is a significant risk factor in whether a child develops autistic characteristics or not.

The researchers have stressed that though they cannot prove testosterone exposure in the womb causes autism, they strongly believe that it could be
the factor that eventually leads to the source of the brain disorder.

Professor Simon Baron Cohen of Cambridge University, the United Kingdom, said 235 healthy children whose mothers had amniocentesis – a womb test during pregnancy – were closely monitored for eight years and tested for autistic-like behavior at regular intervals during their development.

It was found that high levels of testosterone in the amniotic fluid of the womb were significantly correlated with autistic-like behavior, such as whether the child tends to be more unsociable or less empathetic than normal.

Professor Baron Cohen told the British Association’s Science Festival at York University that “it is a significant correlation and it is a correlation that
remains significant after you have controlled for a whole set of other factors.”

Previous work on animals has suggested that testosterone in the womb may affect the early development of the brain, which in humans might lead to the sort of extreme behavior typical of autistic spectrum disorder, including Asperger’s syndrome.

“What we knew before this study was that fetal testosterone was showing a correlation with social development at earlier points in childhood,” Professor Cohen added. “But we hadn’t been able to look at so-called autistic traits before, so in that respect this is something new. The idea that fetal testosterone actually plays a causal role in autism is just a hypothesis. So there is no evidence from any laboratory in the world that this is actually a causal factor, but this research is certainly consistent with that hypothesis.”

Professor Baron Cohen has pioneered the ‘extreme male brain’ theory to explain that autism and its related disorders may be a manifestation of being at the end of a wide spectrum of behaviors seen typically in little boys rather than little girls.

Autistic characteristics, for example, includes a fascination with numbers and systems – such as collecting cards – rather than conversational play with other children, which typifies the sort of behavior seen more commonly in small girls.

Children with autism seemed to have an exaggeration of the typical male profile because they have a very strong interest in systems, like numbers, but have difficulties with empathy, according to Professor Cohen.

Cases of autism – or, more accurately autistic spectrum disorder – have increased dramatically over the past 30 years. But experts say that this is
almost certainly on account of better diagnosis and a broadening of the definition to cover other conditions, rather than a real increase in the number of autism cases.