Aside from several distinct single-gene disorders such as fragile X and Rett syndromes, most forms of autism are thought to arise from a complex interplay between inherited variations in potentially dozens of neurological genes and environment-driven changes in gene expression – aka epigenetics – and chemical signaling. And though scientists previously examined the possible influence of environmental factors after birth (like the thoroughly discredited link to vaccines), more recent research has indicated that autism spectrum disorder (ASD) is set in motion during prenatal development, and a long list of in-utero exposures have been implicated.
One emerging theory suggests that elevated levels of androgens – steroid hormones that contribute to male sexual characteristics – produced by the mother play a large role.
Now, a study from the University of Cambridge’s Autism Research Centre adds further weight to this link with the finding that women with polycystic ovarian syndrome (PCOS) are more likely to have children with ASD and to have autism themselves. PCOS is a common yet poorly understood condition wherein a woman’s ovaries secrete abnormally high amounts of androgens, causing metabolic dysfunction from insulin resistance and preventing the fluid-filled multicellular sacs that are meant to release an egg cell each menstrual cycle from maturing correctly.
The results, published in Translational Psychiatry, were drawn from an analysis of medical records from more than 26,000 UK women diagnosed with PCOS symptoms.
"This new research is helping us understand the effects of testosterone on the developing fetal brain, and on the child's later behaviour and mind," senior author Simon Baron-Cohen said in a statement. “These hormonal effects are not necessarily independent of genetic factors, as a mother or her baby may have higher levels of the hormone for genetic reasons, and testosterone can affect how genes function."
In the first two parts of the three-part study, Baron-Cohen and his colleagues assessed the prevalence of PCOS in 971 women with ASD and the prevalence of ASD in 26,263 women with PCOS, compared with more than 130,000 control women of matched ages and residence locations. The number-crunching revealed that ASD women were more than twice as likely as non-ASD women to have PCOS, though the risk for both was low (2.3 vs 1.1 percent).
And the rate of ASD in women with PCOS was nearly twice that of non-PCOS women (0.17 vs 0.09 percent). It must be noted, however, that this calculation was not adjusted for confounding by other psychiatric conditions.
During the last part of the data analysis, the authors revealed that the children (8,588) born to women in the group of PCOS women were 35 percent more likely to have autism than the 41,127 matched controls, after adjusting for pregnancy complications and the mother’s psychiatric and metabolic conditions. The pattern held true for both male and female children (ASD is over four times more common in boys). Unfortunately, this section of the analysis did not account for ASD risk factors potentially inherited from the father.
In light of these associations, and similarly strong ones found in a Swedish study conducted at the same time, Baron-Cohen’s team recommends that infants born to mothers with PCOS symptoms should be carefully monitored for ASD, as early psychological intervention can help circumvent social deficits if they do turn out to have some form of the condition.
Of course, because PCOS can have a variety of different effects on the body, the team concedes that it is too soon to say that steroid hormones alone are responsible for altering a fetal brain.
“Although it is particularly difficult to tease apart obesity, hyperinsulinemia, and hyperandrogenemia, given they are so intricately intertwined, the association of all three with both autism and PCOS increases the likelihood of a related mechanism,” they wrote.