Children are ten times more likely to be diagnosed with autism if they have a brother or sister with the developmental disorder, researchers at King’s College London found.
For the first time, researchers have been able to quantify the risk so that parents can make a decision about extending their families.
In the general population, autism affects approximately 1 in 100 children.
However In the biggest ever study of its kind, academics found the risk is 10.3 times greater if a sibling has the condition. The risk also triples if they have a half-brother or sister and doubles if they have a cousin with autism
We would normally say “Aha! genetics!” at this point. So, therefore it’s not MMR and all that.
However, it all gets a bit more complicated if we’re trying to decide between straight genes and uterine development. There’s a strand of thought that the cause is not in fact straight genes, but rather to do with floods of hormones through the developing brain. And if that is so then the higher likelihood in a second pregnancy is not a killer diagnosis of it all being purely genetic.
Or, of course, if there’s an environmental cause for that flood of hormones then that could be evident on subsequent pregnancies.
The cousins bit does point to genetics, but the second gravidae part is still inconclusive.
All rather complicated and of course I know very little about this. But it does rather interest that there are others looking at gayness and coming to similar conclusions, that it’s about development in the womb not genes. I have a feeling that this is going to become a lot more important, the study of not just genes, but their expression during pregnancy, as an explanation for all sorts of things.
Genes might indeed explain such things as hair colour, eye colour, but more complex things are going to end up being explained (perhaps, see above I know nothing) as the interaction of these with the developmental environment.