Socio-economic determinants of drugged driving – a register-based study Karoliina Karjalainen 1 , Tomi Lintonen 2,3 , Antti Impinen 1 , Pirjo Lillsunde 1 , Pia Mäkelä 1 , Ossi Rahkonen 4 , Jari Haukka 1,4 & Aini Ostamo 1,3 National Institute for Health and Welfare, Helsinki, Finland, 1 The Finnish Foundation for Alcohol Studies, Helsinki, Finland, 2 School of Health Sciences, University of Tampere, Finland 3 and University of Helsinki, Department of Public Health, Helsinki, Finland 4 ABSTRACT Aims To examine the associations between socio-economic characteristics and driving under the influence of drugs (DUID), and to elaborate determinants of drugged driving. Design A register-based case–control study. Setting Fin- land. Participants Cases (n = 5859) apprehended by the police and suspected of DUID during 1993–2006 and controls (n = 74 809) drawn from the general Finnish population. Measurements The effects of parents’ and own education, urbanization of municipality, socio-economic position (SEP), main activity, income, marital status and living arrangements on DUID were estimated using logistic regression analysis. The analyses were conducted sepa- rately for men and women, age groups of under 45 years and aged 45 or over, and for substance groups of benzodi- azepines only, benzodiazepines with alcohol, amphetamines and cannabinoids. Findings Low education, unemployment, disability pension, being divorced and living alone were the strongest individual predictors of DUID in all substance groups. Illicit drug users were more disadvantaged compared to those in the benzodiazepines groups. Contrary to other substance and age groups, higher educational level and higher SEP were associated with DUID among benzodiazepine users aged 45 or over. Conclusions A disadvantaged social background is a significant pre- dictor of driving while under the influence of drugs for all substance use groups in Finland. The gradient is greater for amphetamines and cannabinoids than benzodiazepines. Keywords Amphetamines, benzodiazepines, cannabinoids, driving under the influence of drugs, register-based study, socio-economic determinants. Correspondence to: Karoliina Karjalainen, National Institute for Health and Welfare, PO Box 30, FI-00271 Helsinki, Finland. E-mail: karoliina.karjalainen@thl.fi Submitted 31 May 2010; initial review completed 5 August 2010; final version accepted 25 February 2011 INTRODUCTION Driving under the influence of drugs (DUID) poses a con- siderable threat to traffic safety [1–3]. In addition to risking other people’s health, drugged drivers can also harm themselves: their risk of premature death has been shown to be high [4–6]. Socio-economic inequalities in health are widely rec- ognized [7]. There are socio-economic differences, for example, in mortality and morbidity [8], and differences have been found similarly with regard to drug use. The association between social background and illicit drug use has been studied among samples from general popu- lations [9–11], drug treatment programmes [12–14] and those outside treatment [15]. These studies have shown that a disadvantaged social background (e.g. lower education, lower income, unemployment) and social marginalization (e.g. homelessness or incarceration) are associated with illicit drug use. Similarly, disadvantaged social background is associ- ated with the use of legal prescription drugs, for example benzodiazepines. Population-based studies have shown that, for example, lower education, lower income, unemployment, being divorced or widowed or being on a disability pension predict current or long-term benzodi- azepine use [16–20]. Some of these associations, however, attenuate or disappear after controlling for health status [16,17]. Social factors exposing to DUID have barely been studied, but some evidence exists. For example, a RESEARCH REPORT doi:10.1111/j.1360-0443.2011.03422.x © 2011 The Authors, Addiction © 2011 Society for the Study of Addiction Addiction, 106, 1448–1459