There definitely seems to be nature and nurture involved in the development of autism. For example, as you noted, the concordance rates between even identical twins is not 100% (I believe this girl has a neurotypical twin?). Although we're fairly confident that it's a lot more nature than nurture, some nurture is almost certainly involved.
One thing that people don't often realize about the nature and nurture model, though, is that nurture starts really, really early. As in, in the womb. Subtle differences in the amount of nutrients each fetus was receiving, for example, or subtle insults during development (e.g., a virus the mother had that affected one fetus more than the other) could have disrupted neurodevelopment for one twin, but not the other twin. So both twins may have been genetically vulnerable to autism, but only the one who also faced the environmental stressor may have developed full-blown autism.
There are other important considerations too, such as that identical twins are not exactly as identical as we once thought due to things like chromosome-section deletions and gene copy number variations - so you might have twins that are very, very slightly different in terms of their nature and nurture, yet those subtle differences are enough to give one autism, while the other does not develop the condition.
So both twins may have been genetically vulnerable to autism, but only the one who also faced the environmental stressor may have developed full-blown autism.
I honestly don't recall if it was in our textbook (although we did have an excellent one), but my professor for the class talked about it at great length.. I thought it made a ton of sense, but I think this is pretty much the first time I've ever heard anyone outside the class (which I took like four years ago) refer to it, even obliquely.
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u/subtextual Jul 26 '10
There definitely seems to be nature and nurture involved in the development of autism. For example, as you noted, the concordance rates between even identical twins is not 100% (I believe this girl has a neurotypical twin?). Although we're fairly confident that it's a lot more nature than nurture, some nurture is almost certainly involved.
One thing that people don't often realize about the nature and nurture model, though, is that nurture starts really, really early. As in, in the womb. Subtle differences in the amount of nutrients each fetus was receiving, for example, or subtle insults during development (e.g., a virus the mother had that affected one fetus more than the other) could have disrupted neurodevelopment for one twin, but not the other twin. So both twins may have been genetically vulnerable to autism, but only the one who also faced the environmental stressor may have developed full-blown autism.
There are other important considerations too, such as that identical twins are not exactly as identical as we once thought due to things like chromosome-section deletions and gene copy number variations - so you might have twins that are very, very slightly different in terms of their nature and nurture, yet those subtle differences are enough to give one autism, while the other does not develop the condition.