A study of twins shows that autism is largely genetic
In the fight against misinformation about autism it seems science is starting to come out on top, finally. A new study hopes to add to the recent advancements made in the understanding of autism, which finds that a substantial genetic and moderate environmental influences were associated with risk of autism spectrum disorder (ASD) and broader autism traits in a study of twins.
Much of the evidence to date highlights the importance of genetic influences on the risk of autism and related traits. But most of these findings are drawn from samples of individuals which may miss people with more subtle manifestations and may not represent the broader population, according to the study background.
In this study the researchers examined genetic and environmental factors for risk of ASD and related traits from a population-based sample of all the twin pairs born in England and Wales from 1994 through 1996. The twins were assessed using several screening instruments: the Childhood Autism Spectrum Test (6,423 pairs), the Development and Well-being Assessment (359 pairs), the Autism Diagnostic Observation Schedule (203 pairs), the Autism Diagnostic Interview-Revised (205 pairs), and a best-estimate diagnosis (207 pairs). Importantly, the study included twins with high subclinical levels of autism traits and low-risk twins, as well as those diagnosed with ASD.
The authors found that on all ASD measures, associations among monozygotic (identical) twins were higher than those for dizygotic (fraternal) twins, resulting in heritability estimates of 56 percent to 95 percent. The analyses highlight the importance of genetic factors in the cause of ASD along with moderate nonshared (different experiences among children in the same families) environmental influences, according to the study.
“We conclude that liability to ASD and a more broadly defined high-level autism trait phenotype in U.K. twins 8 years or older derives from substantial genetic and moderate nonshared environmental influences,” the study concludes.
It’s important to remember that this says nothing about the genetics of the parents as (it is thought) that most instances of autism is caused due to a de novo mutation — a fancy way of saying a new (random) mutation in the DNA of a sperm or an egg. Now keep in mind we constantly are mutating, our DNA gets copied over and over meaning errors are going to happen no matter what you do.
Most mutations you will never notice — the mutation has no effect, the cell dies because the mutation causes the cell to not function properly, or some other change that does not matter in the day to day function of the cell. However, as mutations accumulate in our DNA things inevitably change, this gives rise to things like cancer, or in this case autism.
In the case of a mutation that leads to autism, it just happens to be a sperm cell that has the mutation. In contrast, the same mutation in a red blood cell would have no effect on a child nor the parent that had the mutation.
Mutations are a tricky thing though since there is a lot of things that can cause them, thankfully (and anyone who knows my blog probably saw this coming) your normal immune system responses cannot cause mutations, this means that vaccines do not cause autism, nor do they cause any sort of mutation. Rest assured that this has been proven over and over again in science and a search of peer reviewed works will show you just that.
A interesting note that needs to be made, autoimmune diseases can, in fact, cause mutations because the immune system destroys healthy tissues in the body, meaning they need to be replaced faster than normal. This allows for more mutations to come about from the accelerated upkeep the body has to take on. While this is a indirect cause, it is important to point out.
Lastly, there is no “cure” for autism. For parents of autistic children, it can be scary at first, but autistic children are just as amazing and unique (if not more so) than an average child. The knee-jerk reaction is usually to blame yourselves, or figure out what you did “wrong,” rest assured that you did nothing wrong and that your child can be as healthy and happy as any other child.
The most important thing is to just love them and learn how they think to help them develop skills needed for life. Truthfully, if you are a parent of an autistic child and you are reading this because you genuinely care and are searching for more information, then you obviously love your child and are doing everything as right as any parent could possible do. In short, be easy on yourselves, you’re doing just fine.
Colvert, E., Tick, B., McEwen, F., Stewart, C., Curran, S., Woodhouse, E., Gillan, N., Hallett, V., Lietz, S., Garnett, T., Ronald, A., Plomin, R., Rijsdijk, F., Happé, F., & Bolton, P. (2015). Heritability of Autism Spectrum Disorder in a UK Population-Based Twin Sample JAMA Psychiatry DOI: 10.1001/jamapsychiatry.2014.3028