Maternal Age and Autism Risk: Exploring Key Variables

Introduction: Rising Autism Diagnoses

One of the most alarming trends in psychology is the increase in diagnoses of autism spectrum disorder. No singular cause has yet been determined to explain why autism rates have risen so rapidly, although most scientists believe that improved screening efficacy cannot entirely account for the spike in cases. A correlation between the age of the mother and the likelihood of a child developing autism has been observed. As De Noon (2010) notes, "the older a mother is when she gives birth, the higher her child's risk of autism."

Specifically, "women over age 40 are 77% more likely than women under age 25 to have a child with autism," while "women under age 25 are 14% less likely than women aged 25–29 to have a child with autism" (De Noon, 2010). The correlation between a father's age and the likelihood of a child developing autism was less pronounced, appearing most clearly "when the child is born to a father over age 40 and a mother under age 30" (De Noon, 2010).

Maternal Age and Autism Risk

The reasons for the correlation between maternal age and autism risk remain unclear. One hypothesis is that age-related changes in the parents' genetic makeup make their offspring more vulnerable to autism. A separate line of research found that "some mothers of children with autism had antibodies to fetal brain protein, while none of the mothers of typical children did," and the production of such antibodies tends to increase with age (Autism rates much higher in children with older moms, 2012). These excessive antibodies may interfere with normal fetal brain development in older mothers' offspring.

Hypotheses Explaining the Correlation

Several hypotheses have been proposed to explain why older parents are more likely to have children with autism. One possibility is the buildup of environmental toxins in the body over time, which may increase the likelihood of autism in offspring. Another possibility is that individuals who are genetically predisposed toward autism — which can manifest as mild social impairment — may tend to marry later and have children later. Autism is characterized by impairment of normal social functioning, and quite often one or both parents may exhibit a milder form of the disorder while their child expresses the full condition.

To further complicate the picture, scientists note that overall increases in autism rates cannot be explained by delayed childbearing alone. "This trend accounts for less than 5% of the autism increase in California over the decade 1990–1999 … Parental age is just one risk factor that is interacting with other genetic and environmental factors that lead to a child developing autism" (De Noon, 2010). Parental age, therefore, may function less as a direct cause and more as a clue pointing toward deeper environmental or biochemical factors that are simply more prevalent among older parents.

Conclusion

Statistics about the interaction between maternal age and the likelihood of developing autism should not be used to blame older mothers. Rather, they should be seen as a source of possible information about an as-yet unknown significant variable present within that demographic that could influence the development of the disorder. Understanding autism risk factors requires examining the full constellation of genetic, environmental, and developmental influences — of which parental age is only one piece.

References

Autism rates much higher in children with older moms. (2012). Live Science. Retrieved from http://www.livescience.com/6080-autism-rates-higher-children-older-moms.html

De Noon, D. (2010). Autism risk rises with mother's age. WebMD. Retrieved from http://www.webmd.com/brain/autism/news/20100208/autism-risk-rises-with-mothers-age