Is socioeconomic status in early life associated with drug use? A systematic review of the evidence JAMES Z. DANIEL 1,2 , MATTHEW HICKMAN 3 , JOHN MACLEOD 4 , NICOLA WILES 1 , ANNE LINGFORD-HUGHES 1 , MICHAEL FARRELL 5 , RICARDO ARAYA 1 , PETROS SKAPINAKIS 1 , JON HAYNES 1 & GLYN LEWIS 1 1 Academic Unit of Psychiatry, University of Bristol, Bristol, UK, 2 Centre for Appearance Research, School of Psychology, University of theWest of England, Bristol, UK, 3 Department of Social Medicine, University of Bristol, Bristol, UK, 4 Department of Primary Care and General Practice, University of Birmingham, Birmingham, UK, and 5 National Addiction Centre, Institute of Psychiatry, London, UK Abstract Aim. To conduct a systematic review of longitudinal studies that examined the association between childhood socioeconomic status (SES) and illegal drug use in later life. Design and Methods. Systematic search with an agreed list of search items was used to identify all longitudinal population-based studies that examined the association between childhood SES and later drug use. These included MEDLINE (1966–2005), EMBASE (1990–2005), CINAHL (1982–2005) and PsychInfo (1806–2005), and specialist databases of the Lindesmith Library, Drugscope and Addiction Abstracts. Foreign-language papers were included. Abstracts were screened independently by two reviewers. If there was disagreement to accept or reject the abstract, then a third reviewer acted as arbiter. Data were extracted by one of the authors. Results. Eleven relevant papers were identified (two birth cohorts and nine papers on school-aged cohorts). There was consistent evidence to support an association between lower childhood SES and later drug use, primarily cannabis use. However, few studies examined cannabis dependence, and studies of more problematic forms of drug use gave contradictory results. Discussion and Conclusions. We found consistent, though weak, evidence to support the assumption that childhood disadvantage is associated with later cannabis use. Further research is needed to clarify this issue and to inform future policies and public health messages. [Daniel JZ, Hickman M, MacLeod J, Wiles N, Lingford-Hughes A, Farrell M, Araya R, Skapinakis P, Haynes J, Lewis G. Is socioeconomic status in early life associated with drug use? A systematic review of the evidence. Drug Alcohol Rev 2009;28:142–153] Key words: social class, socioeconomic factor, drug use, cannabis, systematic review. Introduction A causal relation between social disadvantage and illicit drug use is often assumed. For example, a report from the UK Advisory Council on the misuse of drugs con- cluded that ‘deprivation . . . is on the balance of evi- dence significantly and causally related to problematic drug use’ [1]. Such conclusions, though clearly plau- sible, have a limited empirical basis. Moreover, they are substantially based on cross-sectional data on adults with deprivation often measured at the ecological rather than individual level. Such data cannot strongly support conclusions around causality in individuals. The question of causality is of considerable impor- tance. If deprivation in early life is an important cause of problematic drug use, then interventions to reduce disadvantage should be part of strategies to reduce drug-related harm. The issue is also relevant to epidemiological inves- tigations into the consequences of drug use. Social disadvantage, particularly in the early life course, is associated with increased risk of many unfavourable James Z. Daniel PhD, Matthew Hickman PhD, FFPHM, John Macleod PhD, MRCGP, Nicola Wiles PhD, Anne Lingford-Hughes PhD, MRCPsych, Michael Farrell MB BCh, FRCPsych, Ricardo Araya PhD, MRCPsych, Petros Skapinakis PhD, Jon Haynes MB BCh, MRCPsych, Glyn Lewis PhD, FRCPsych. Correspondence to Dr Matthew Hickman, Department of Social Medicine, University of Bristol, Bristol, BS8 2PR, UK. Tel: +44 (0)117 928 7252; Fax: +44 (0)117 928 7325; E-mail: matthew.hickman@bristol.ac.uk Received 8 February 2007; accepted for publication 1 August 2008. Drug and Alcohol Review (March 2009), 28, 142–153 DOI: 10.1111/j.1465-3362.2008.00042.x © 2009 Australasian Professional Society on Alcohol and other Drugs