Posted by Larry Hoover on March 4, 2007, at 12:01:45
In reply to Re: hmm, well - » Larry Hoover, posted by one woman cine on March 4, 2007, at 11:15:34
> hey larry, thanks for the link - however I read the whole article - that's just the abstract (on an article written 7 years ago - so it's on the "old side")
The subject selection arises from twin registries, which IMHO aren't subject to staleness issues. And SCID-2 is pretty well validated. Statistical methods haven't changed in the meantime. Only if there was now a better psychometric would I be concerned with date.
I wish I had access to the whole article. There are always hidden considerations.....often ones that turn the whole thing on its head. Anyway, I'm stuck with the abstract.
> from the abstract -
Further excerpted....
> "PDs seem to be more strongly influenced by genetic effects than almost any axis I disorder, and more than most broad personality dimensions. However, we observed a large variation in heritability among the different PDs, probably partly because of a moderate sample size and low prevalence of the specific disorders."
Which I read to mean: Collectively, the genetic/PD correlation is strong, whereas individually the correlations are weaker due to insufficient data points.
> I think the thrust is not necessarily genetic, but environmental for PD's - I think as I mentioned - they have also stated that there sampling size was "moderate" and biased (low prevalence) in disorder type.
They couldn't exclude environment, true. It was inconsistent with the data, nonetheless. "The best-fitting models never included shared-in-families environmental effects."
> That does not necessarily mean that it's genetic -the study points to the possibility - but many things are possible, though not probable.
That's what heritability estimates are, of course. The environmental influences are factored into the value obtained; it is the relative proportion of genetic variation to environmental variation that is expressed in one statistic. From wiki: "Heritability only quantifies how much of the total phenotypic variation in a population is attributable to variation among individual genotypes compared to the variation in the their environment."
Put another way, h² > c², and, e² was small. See: http://en.wikipedia.org/wiki/Heritability#Twin_studies
Putting the heritability estimates here obtained into context, they exceed those for schizophrenia, and are similar to those for mood disorders. They are substantially higher than those obtained for introversion/extroversion (to use a personality variable).
Imputing meaning or sociological significance to these statistics is certainly a subjective exercise.
Lar
poster:Larry Hoover
thread:737579
URL: http://www.dr-bob.org/babble/social/20070223/msgs/738202.html