Nat. Genet. 41, 991–995 (2009); published online 2 August; corrected online 23 August 2009

In the version of this article initially published online, Simonetta Guarrera and Silvia Polidoro were inadvertently omitted from the author list, and an affiliation was omitted for Paolo Vineis. These errors have been corrected in all versions of this article.