> Obese parents, both mum and dad, multiply the likelihood of child autism by something like 4x. It could be that the obesity epidemic is the cause of the rising autism rates.
Even assuming the first sentence is correct going from 0% prevalence to 100% prevalence of something with a 4x risk increase would explain only a very small part of the increase in the various proxies by which the prevalence is estimated, whereas (as the article argues) change in diagnostic criteria and reporting practices can easily explain all of it. So, sure, to the extent there is any real increase in prevalence (which is not at all clear), factors like parental obesity, parental age, and other things that have some indication of being either risk factors or proxies for unidentified risk factors may either play a role or be indicative of things that do, but we can be fairly certain what the main driving factor in the numbers is, and it is sufficient to explain the observations, and invoking anything else is a violation of the principal of parsimony.
Even assuming the first sentence is correct going from 0% prevalence to 100% prevalence of something with a 4x risk increase would explain only a very small part of the increase in the various proxies by which the prevalence is estimated, whereas (as the article argues) change in diagnostic criteria and reporting practices can easily explain all of it. So, sure, to the extent there is any real increase in prevalence (which is not at all clear), factors like parental obesity, parental age, and other things that have some indication of being either risk factors or proxies for unidentified risk factors may either play a role or be indicative of things that do, but we can be fairly certain what the main driving factor in the numbers is, and it is sufficient to explain the observations, and invoking anything else is a violation of the principal of parsimony.