Diagnosis of autism spectrum disorders have been on the rise for some time, and quite a bit of research has been devoted to understanding the mechanisms of autism. One of the more widely known aspects is the discovery that males are affected more significantly than females. Is the autism rate truly higher in boys than in girls, or is the diagnosis being missed in females for some reason?
According to research recently published in the American Journal of Human Genetics, it is not a misdiagnosis-autism really does occur less often in girls than in boys. The research team, led by geneticists at the University of Washington, studied over 16,000 people and determined that there was a gender gap of nearly seven to one, with males being diagnosed more often than females.
However, at the more severe end of the autism spectrum, the gender gap is considerably smaller. The research team believes that this implies that boys are simply more susceptible to autism than girls, and that fewer factors are necessary to instigate at least mild autism-but when enough factors are present to cause autism in girls, the effect is more severe.
Another finding of the study was that genetic mutations that cause autism, if they did not come from the child directly, were more likely to be contributed by the mother than the father.
A man with a significant autism-related genetic trait is more outwardly affected by it, and is therefore more likely to have difficulty in meeting and developing relationships with potential mates. Consequently, they are less likely to reproduce and past the traits on. Women, on the other hand, are less likely to be outwardly affected by any milder autism-related genetic mutations, and therefore are more likely to find mates, reproduce and pass the genes on to their children.
Why is this important? Consider that a genetic mutation responsible for autism could come from either parent, or it could be a mutation that neither parent has. If you are a couple with an autistic child and trying to decide whether to have more children, you are very interested in knowing whether your child's autism can be traced back to a genetic factor that either parent possesses. Such a connection doesn't mean that a second child is certain to have autism, but it does raise the risk. Families can weigh whether that risk is worth taking in their case.
While genes play a role, they don't necessarily tell the whole story. Environmental factors may play a role, whether primary or supplementary. One such theory is that the testosterone levels that boys are exposed to in the womb is significantly higher than that of girls, and that this may play a role in the higher sensitivity of males to autism development if the correct genetic mix is present.
At this point, there are around 500 different genes that have been connected to disorders in the autism spectrum, but many of the genes affect the development of autism in a similar fashion. There are an estimated 12 different genetic pathways of autism development. Hopefully, research like this will continue to narrow and define those pathways so effective treatments can be discovered for the genetic component of autism disorders.