Genetics Or Environment?
The debate rages on; is autism an inherited (genetic) condition or is it caused primarly by environmental factors?
A recent study in California looked at sets of twins with autism. The researchers looked at both identical twins and fraternal twins (non-identical). In identical twins the DNA is identical between the twins, whereas in fraternal twins only half the DNA is shared.
If autism was primary a genetic condition then one would expect identical twins, who have identical DNA, to both be autistic whilst fraternal twins would have a much lower ratio of autistic to non-autistic twin.
Conversely if autism was primarily an environmental condition then one would expect the fraternal twins and identical twins to have similar ratio of autistic to non-autistic twins.
What the researchers found was that there appeared to be a significant genetic contribution to whether both twins would be autistic; however there was a greater environmental component in determining if both twins were autistic. based on their findings the authors calculate that
shared environment accounts for 55% of the risk of autism and 37% for genetic heritability.
There’s an abstract of the report in the Archives of General Psychiatry or, if you’d like to read a fuller discussion, please see Genetic Heritability and Shared Environmental Factors Among Twin Pairs With Autism on Left Brain Right Brain.
Weekly Round-Up
One thing that never ceases to amaze me about the autistic spectrum is the huge amount of research, theorizing, speculation that’s published each week on the subject. I think it reflects how little we really do know about the condition from one end of the spectrum to the other.
While genetics are thought to play a role in autism there’s also a lot of people who will argue that the large rise in autism diagnoses has to be due to some environmental factor. I found an article, ‘Environment’ Poses a Knotty Challenge in Autism, that gives an interesting discussion on what ‘environment’ means in the context of autism.
When I was in my early 20′s (a looooong time ago) any discussion around becoming a parent would usually visit the topic; to vaccinate or not to vaccinate. This related to the research put forward by Dr Andrew Wakefield who suggested a link between the MMR vaccine and autism. Dr Wakefield’s research has since been thoroughly discredited; but his legacy lingers on in peoples minds and I get the feeling that researchers may be reluctant to reopen the vaccination debate. However Helen Ratajczak has undertaken a review of a wealth of credible published scientific research that suggests that vaccines may, indeed, play a part in the development of autism. There’s further comment in How to Help Eliminate the Hidden Enemy that Triggers Autism where it’s argued that a vaccine may act as a precursor to other events leading up to the autistic condition.
So the debate continues as we try to unravel the autistic spectrum. How many of you think that environment or vaccines have a significant role in the development of autism?