What doesn't kill you makes you dumber
The idea that infectious disease during childhood affects the developing brain to impact intelligence has been around for decades. Recent evidence from more rigorous studies, which have controlled carefully for other factors such as nutrition and education, has strengthened the case.EMBO reports 13, 193 - 196 (10 February 2012) | doi:10.1038/embor.2012.13
http://www.nature.com/embor/journal/v13/n3/full/embor201213a.html