1Note: The contents of this paper, including data, analysis, interpretation and presentation are the responsibility of the authors and not of the United Nations.
2the Centre for Research on Drugs and Health Behaviour (CRDHB), Department of Primary Care and Social Medicine, Imperial College, London, UK.
3to Carmen Aceijas, Centre for Research on Drugs and Health Behaviour, Imperial College, Faculty of Medicine, St Dunstan's Road, London, W6 8RP, UK.