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It's All Relative: The Genetics of Autism in Families

The genetics of Autism

Increasingly each day the parents of autistic children are finding out they're also Aunts and Uncles to autistic nieces and nephews. The numbers are staggering. It has happened in my family multiple times. Each diagnosis I am told about is received with the same shock as I felt when I found out my son had been diagnosed. It never gets easier to accept; however, the diagnosis does get easier to explain. It suddenly becomes easier to relate to your relatives. The genetics of Autism, however, is a little bit more complicated than just simply saying it “runs in my family.”


There are several studies out that point towards a genetic link in the diagnosis of Autism. It was like so in my immediate family. My son and husband share the same chromosomal duplication. Finding out was a double-edged sword. We had searched for answers for so long yet didn’t expect the ones that we got.

My husband has since found out that he has Autism and went most of his life undiagnosed. The confusion associated with finding out something like that at maturity is not something that I personally can wrap my mind around. As far as the genetics of Autism goes, I’d like to point your attention to two studies. One on the Parental links and one on twins.


The first being that done on twins. A study of 258 twins done by the Medical Research Council in the United Kingdom found that 56 percent - 95 percent of the effect is estimated to be genetic. Researchers found that one way they could control for the effect of genes while they were doing research on Autism is to look at “genetically homogeneous groups,” or twins.

The use of “monozygotic twins and dizygotic twins” in this study gave researchers a unique aspect that other studies did not have. Studying twins allowed them to study pairs that were raised in the same household with the same parental figures. It also allowed them to look at prevalence rates of Autism while also having pairs of twins exposed largely to the same environmental factors. If you’re looking at 1000s of Autistic individuals in different homes, you must account for tons of different environmental factors. This way they did not have to do that. They had the control of them being in the same household.

If you want to break the numbers down further, the study found a larger genetic link between twins than one would expect. In fact, it is said that “if one identical twin has autism spectrum disorder, the other twin has a 76 percent chance of also being diagnosed with it.” The study did point out that the numbers were lower for fraternal twins. The percentage of fraternal twins who each share an ASD diagnosis is 34 percent for same-sex twins and 18 percent for boy-girl pairs.

It is important to comment that the authors of this twin study found a significant effect of environment on the diagnosis of Autism. The effect of environment was about one-half to one-third as compared to the genetic effect. As Dr. Judith Brown, of the UK's National Autistic Society noted, "We are still a long way from knowing what leads to autism. Autism is a highly complex story of genes not only interacting with other genes, but with non-genetic factors too.”

Parental Links

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Another small study really caught my attention. It was on the paternal link to Autism. It was published online in the International Journal of Epidemiology early in 2016. The study found a possible association between the disorder and a father’s “epigenetic tags, which help regulate genes’ activity. Per the Genetic Literacy Project, researchers “identified more than 190 sites where the presence or absence of a tag was statistically related to whether the father’s child would show early signs of autism.” This points at signs of us being able to test for the passing of Autism through a father’s sperm. As Professor Daniele Fallin said (co-lead investigator, professor and chair of the Department of Mental Health in the Bloomberg School of Public Health), "If epigenetic changes are being passed from fathers to their children, we should be able to detect them in sperm."

Per the same source, there has also been “novel research looking at blood-based biomarkers to identify autism spectrum disorder.” Find “quantitative biomarkers” for any given disease state is described as being the “holy grail of medicine.” Of course the science isn’t complete yet and in the spirit of science, may never be done. Researchers work tirelessly on these things, to get answers for us. It is important to also point out that this current research has only been “performed in male infants and toddlers, and it’s currently estimated to be accurate about three-quarters of the time.” One thing is for sure. No matter what the research tells us, each diagnosis is different for each family. Each diagnosis initiates a new member into a new club. The Autism Club, sometimes that Club is just full of family members.

Finding the Genes

Per Stanford at The Tech Museum, scientists have found that 20 out of 23 chromosomes have regions that may be important for Autism. As they say, having so many genetic candidates make it hard to find single autism-linked genes. Stanford points out that this is often because of the way scientists usually find disease genes.

To break it down for you, what they tend to do is look at the DNA of lots of people with a disease or disorder, like Autism. They then compare it to close relatives who don't have the disease. By such on tons of families, scientists can figure out where important changes are. What makes it harder is when there is more than one gene, as with Autism. The research here is useful in finding autism-linked genes however, because it can show scientists where to look in the DNA, per Stanford at The Tech Museum. Scientists can focus on those areas where they found the changes in other autistic families.

The "Club"

What do you do once a family member has a child diagnosed? Well, you welcome them to our club. Our "club" isn't one full of massages and mud baths though, our "club" in one of bags under our eye's and the amazing ability to operate on 2 hours of sleep. Our club consists of the toughest of the tough; the elite 1 in 68. Each new diagnosis sends a new family into overdrive and overcomes said family with questions and worry. The diagnosis tends to leave more questions than it gives answers. When the answer is a genetically linked one the shock can be even more extreme. Be mindful of that.

When family members have children diagnosed [after our children] it's hard to remember that we were once at the beginning stage too; whenever they have children diagnosed before our children it's next to impossible to empathize with that parent, that family member. It's impossible to know that there is a state of shock that overcomes one after the initial diagnosis, it's easy to hurt the feelings of others.

When it comes to hurt feelings, you must remember these "newly diagnosed" parents earned the right to be less than careful with their words. If they want to ask a million times how their baby will ever live a normal life, let them; make sure you remind them there is no such thing as a normal life, each life is unique. When the parent is compelled to place pity on their child for Autism having suddenly "taken their life from them" it's OK, let them; meanwhile making sure to tell them you used to think the same thing and they'll find their answer in their own time. When they need a shoulder to cry on, be that shoulder... when they need 2am advice on how to ease their child back to sleep, be that voice that laughs on the other end of the line and tells them to turn the coffee pot on.... If they blame themselves over the genetics, remind them that they had no control over that and it isn’t their fault. Be there for your family and love them unconditionally.

When they need courage and strength, lend them yours... Remember when it comes to Autism, often it is all relative.