Preliminary results from the California Autism Twin Study

The IMFAR abstract book is now available:

http://imfar.confex.com/imfar/2010/webprogram/start.html

The CATS study has released a preliminary result and reported that 59.1% of identical twins were concordant for narrowly defined autism.

Three twin studies which have now reported concordance rates for identical twins using a variety of diagnostic schemes and methodologies (population based or parent volunteer based) and have all reported the same consistent,important and startling results. All three studies have reported a consistent 60% concordance rate in identical twins:

Bailey et al 1995 = 60% (narrow definition)
Autism IAN 60.3% (for same PDD diagnosis)
CATS = 59.1% (narrow Definition)

This is an important and consistent finding since 2/3rds of identical twins share a single placenta (same prenatal environment) and are thus equally vulnerable to the consequences of the same prenatal insult. 1/3rd of identical twins develop in seperate placenta and do not share the exact same prenatal environment.

Has the failure of the research community to report concordance rates of identical twins by placentation status led to false impressions and misleading conclusions with respect to the magnitude of the environmental component in Autism?