While the scientific community has completely and repeatedly debunked the ill-conceived notion that vaccines cause autism, it has not been able to definitively answer what does cause autism. According to recent research, it could be due to exposure to certain hormones during pregnancy. A study led Simon Baron-Cohen of the University of Cambridge has revealed a link between fetal exposure to elevated levels of steroid hormones and autism. The results were published today in the journal Molecular Psychiatry.

The study analyzed an astounding 19,500 samples of amniotic fluid from a biobank in Denmark, collected between 1993-1999. The samples were provided by women who chose to have an amniocentesis during the second trimester, around weeks 15-16. This is a busy time for fetal brain development and sexual differentiation.

They identified 128 samples belonging to males who were later diagnosed with autism. The samples were screened for hormone levels, including testosterone, progesterone, and cortisol. Four hormones studied belong to a pathway in which one steroid is synthesized from the one that came before. Samples from the children who had been diagnosed with autism had higher levels of steroid hormones overall when compared to the 217 samples from males without a diagnosis.

“This is one of the earliest non-genetic biomarkers that has been identified in children who go on to develop autism,” Baron-Cohen stated in a press release. “We previously knew that elevated prenatal testosterone is associated with slower social and language development, better attention to detail, and more autistic traits. Now, for the first time, we have also shown that these steroid hormones are elevated in children clinically diagnosed with autism. Because some of these hormones are produced in much higher quantities in males than in females, this may help us explain why autism is more common in males.”

He also stated that “[t]hese new results are particularly striking because they are found across all the subgroups on the autism spectrum, for the first time uniting those with Asperger Syndrome, classic autism, or Pervasive Developmental Disorder Not-Otherwise-Specified. We now want to test if the same finding is found in females with autism.”

‘Great,’ you may be thinking, ‘if they know that elevated hormones may be causing autism, can’t they just do something to turn them off?’ Well, steroid sex hormones are incredibly important to fetal development, and trying to suppress them would likely have permanent devastating side effects. These hormones play an integral role in influencing genetic expression of proteins that help build structures in the brain.

“Our discovery here meshes nicely with other recent findings that highlight the prenatal period around 15 weeks gestation as a key period when important genetic risk mechanisms for autism are working together to be expressed in the developing brain,” said co-author Michael Lombardo.

The researchers also warn that these results do not mean that an amniocentesis can or should be used as a screening test for autism.

“There is considerable overlap between the groups and our findings showed differences found at an average group level, rather than at the level of accurately predicting diagnosis for individuals. The value of the new results lies in identifying key biological mechanisms during fetal development that could play important roles in atypical brain development in autism,” Baron-Cohen explained.

[Header image “Jesica_12” by Molly Darling via flickr, used in accordance with CC BY-ND 2.0]