a1 Division of Clinical Psychology, School of Psychological Science, University of Manchester.
a2 Department of Psychiatry, Manchester Mental Health and Social Care Trust.
a3 School of Psychology, University of Birmingham.
a4 Maternal and Fetal Health Research Centre, Manchester Academic Health Sciences Centre.
a5 Genetic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Sciences Centre.
a6 Department of Biomedical Science, University of Manchester.
(Online publication October 10 2012)