[1] Univ Bristol, Sch Expt Psychol, Bristol BS8 1TU, Avon, England
[2] Univ Bristol, MRC Integrat Epidemiol Unit IEU, Bristol, Avon, England
[3] Univ Bristol, UK Ctr Tobacco & Alcohol Studies, Bristol, Avon, England
[4] UCL, Clin Psychopharmacol Unit, London, England
[5] Imperial Coll London, Dept Med, London, England
[6] Univ Bath, Dept Pharm & Pharmacol, Bath, Avon, England