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Nature vs Nurture: Understanding the Inheritability of Autism

As we’ve continually discussed in this space, research into the cause and treatment of autism often falls into two camps: genetic versus environmental factors. While researchers continue to find new connections between one’s natural environment and its effect on autism, there continues to be study after study that highlights the role that genetics play in the development of autism. This week we will look at a couple of recent studies that attempt to better understand to what degree autism can be inherited from a father or mother.


As a whole, autism spectrum disorder is one of the most heritable neuropsychiatric conditions, but research has largely concerned itself with identifying mutations that occur in individuals well after birth.


However, one recent study is raising the question as to whether a father’s sperm can contain the genetic code that leads to autism. According to investigators at Johns Hopkins School of Public Health in Baltimor, Maryland, the presence of DNA methylation in paternal sperm may be a contributing factor in the development of autism within children.


The researchers discovered nearly 200 regions of methylated DNA in the fathers of children at increased risk of developing autism when the subjects began demonstrating symptoms of ASD at the age of 12 months. While previous studies has looked at the blood of fathers, study author M. Danielle Falin posited that by looking at sperm, researchers could capture a direct snapshot of the genes a father passes on to his children, finding a close relationship in the father’s and child’s DNA.


This finding ended up being somewhat of a fluke as the researchers had started out looking at whether mothers who had given birth to one child with autism were more likely to give birth to siblings with autism.


Another recent study has highlighted the role of mothers in the inheritance of diabetes, finding that diabetes that develops early in a one’s pregnancy may increase women’s chances of having a child with autism. The risk was most prominent in mothers who were diagnosed with diabetes during the most crucial period of fetal brain development.


The researchers looked at medical records for more than 322,000 children born at Kaiser Permanente hospitals in Southern California between 1995 and 2010. Those whose mothers developed gestational diabetes by the 26th week of pregnancy were 40 percent more likely to be diagnosed with autism than those whose moms didn’t have diabetes. Of about 3,400 autistic children, 130 were exposed to diabetes early in pregnancy.


One exception the researchers found was that children whose mothers had either pre-existing diabetes or developed it later in pregnancy were at no increased risk for autism.


While researchers remain uncertain as to the reason behind the potential link, the study’s co-author Dr. Edward Curry at Kaiser Permanente posited that exposure to high levels of blood sugar from a mother disturbs fetal brain growth, particularly in the areas of the brain that are crucial for communication and social behavior.


While neither study establishes a conclusive relationship between which parents are at the highest risk for passing on the genetic code for DNA, both studies have provided crucial insight that will fuel future research into the role that a parent’s genes and medical conditions play in the development of autism in their children.