The published Financial Disclosure is missing funding information. The following is the correct funding information: We gratefully acknowledge the ongoing contribution of the parents and children in the Twins Early Development Study (TEDS). TEDS is supported by a program grant [G0901245; and previously G0500079] from the U.K. Medical Research Council (MRC), with additional support from the US National Institutes of Health [HD044454; HD046167 HD059215]. Genome-wide genotyping was made possible by grants from the Wellcome Trust Case Control Consortium 2 project [085475/B/08/Z; 085475/Z/08/Z]. RP is supported by a Medical Research Council Research Professorship award [G19/2] and a European Advanced Investigator award [295366]; O.S.P.D. is supported by a Sir Henry Wellcome Fellowship from the Wellcome Trust [WT088984]; C.M.A.H. is supported by a research fellowship from the British Academy. We also thank the Wellcome Trust Case Consortium 2 team for their help with genotyping and quality control of our data.