[1] Kings Coll London, Inst Psychiat, Addict Dept, London, England
[2] UCL, Res UK Hlth Behav Res Ctr, Canc Dept Epidemiol & Publ Hlth, London WC1E 6BT, England
[3] Queen Mary Univ London, Barts & London Sch Med & Dent, Wolfson Inst Prevent Med, London, England
[4] St John God Hosp, Dublin, Ireland
[5] Cent & North West London NHS Trust, London, England
[6] South London & Maudsley Hosp Fdn Trust, Addict Directorate, London, England