Autism West Cork

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.