Authors: Paul Ellis; Peter Barrett-Lee; Lindsay Johnson; David Cameron; Andrew Wardley; Susan O'Reilly; Mark Verrill; Ian Smith; John Yarnold; Robert Coleman; Helena Earl; Peter Canney; Chris Twelves; Christopher Poole; David Bloomfield; Penelope Hopwood; Stephen Johnston; Mitchell Dowsett; John M S Bartlett; Ian Ellis; Clare Peckitt; Emma Hall; Judith M Bliss Journal: Lancet Date: 2009-05-16 Impact factor: 79.321