[1] Univ Sussex, Dept Psychol, Brighton, E Sussex, England
[2] Univ Nottingham, Sch Sociol & Social Policy, Nottingham NG7 2RD, England
[3] Univ Oxford, Natl Perinatal Epidemiol Unit, Oxford OX1 2JD, England
[4] Univ Sheffield, Dept Psychol, Sheffield S10 2TN, S Yorkshire, England
[5] Linkoping Univ, Fac Hlth Sci, Unit Hlth Psychol, S-58183 Linkoping, Sweden