[paulfr]

I see the article climbing back up the front page, and I want to make it abundantly clear that I don't believe that there is necessarily a causal relation from breastfeeding vs formula to IQ.

I could control for demographic factors, but not for other major important factors in a child's development -- parental IQ or views regarding parenting are huge factors in a child's IQ, and they may also influence the decision of whether or not to breastfeed. If parenting books unanimously decided that formula was bad, then parents who cared enough about their children to read them and follow their advice would be more likely to breastfeed and you would see a positive correlation with IQ, even if formula was completely equivalent to breastfeeding.

So while there is a clear correlation after controlling for demographic, there is not necessarily a causation. My formulation really wasn't meant to imply causation, but rather the handling of unknown data (I grouped unknown-status children together with breastfed children). When talking about correlation, it's not meaningful to make a distinction between IQ impairment and IQ gain.

[darkmighty]

I really think this shouldn't get this much attention without double blind trials. Specially for a difference as marginal as 1-3 IQ points.