Autism 'caused by genetics', study suggests

[proverbialwisdom]

82. More.

http://www.marthaherbert.org/library/Herbert-Sage-2013-Autism-EMF-PlausibilityPathophysiologicalLink-Part11.pdf

3.1.4. Genetic alterations and reproductive impacts

The overwhelming emphasis in recent decades in autism research has been on genetics, and on finding linkages between genes, brain and behavior, in part because of the high heritability of autism that was calculated from the concordance rates of monozygotic (identical) vs. dizygotic (fraternal)twins found in by a series of small twin studies performed some decades ago. In recent years the genetic premises of this seemingly obvious framing of autism as overwhelmingly genetic have been undermined at several levels (253). First, the number of reported cases is increasing, making it more difficult to maintain that ASCs are purely genetic because these increases can only be partly explained away by greater awareness or other data artifacts (254,255). Second, the complexity of the ways we understand how genes might relate to autism has grown, from an expectation a decade ago that a small number of genes (even less than a dozen) would explain everything to an identification of close to a thousand genes associated with autism with common threads linking only a small subset (256,257), as well as ‘de novo’ mutations present in ASC children but not their parents and even ‘boutique’ mutations not shared beyond an individual family. Moreover, a recent twin study that was much larger than any of the prior such studies identified a modest genetic role but a substantial environmental role (258). Indeed even concordance between identical twins appears to be influenced by whether the twins shared a placenta (259). All of this calls into question the idea that genetics can be presumed to be the ‘cause’ of autism simply based upon heritability calculations, and upgrades the importance of looking not only at the environment and environmentally vulnerable physiology, but also at acquired mutations.

<>