Addictive behaviors and addiction-prone personality traits: Associations with a dopamine multilocus genetic profile Caroline Davis a, ⁎, Natalie J. Loxton b a School of Kinesiology and Health Sciences, York University, Toronto, Canada b School of Psychology, The University of Queensland, Brisbane, Australia HIGHLIGHTS • Dopamine signaling positively influences addictive behaviors. • Personality mediates genetic link to addictive behaviors. • Quantitative genetics a powerful tool for risk-related research. abstract article info Available online 6 March 2013 Keywords: Dopamine Multilocus genetic profile Personality Addictive behaviors The purpose of this study was to examine reward-related genetic risk for addictive behaviors in a healthy community sample (n = 217) of men and women. We tested a mediation model predicting that a quantita- tive multilocus genetic profile score – reflecting the additive effects of alleles known to confer relatively increased dopamine signaling in the ventral striatum – would relate positively to a composite measure of addictive behaviors, and that this association would be mediated by personality traits consistently associated with addiction disorders. Our model was strongly supported by the data, and accounted for 24% of the vari- ance in addictive behaviors. These data suggest that brain reward processes tend to exert their influence on addiction risk by their role in the development of relatively stable personality traits associated with addictive behaviors. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction The estimated heritability of drug dependence and alcoholism is approximately 50%, indicating that genetic and environmental risk fac- tors play a roughly equivalent role in their development (Buscemi & Turchi, 2011; Enoch, 2012). Moreover, the latter appears to be more in- fluential during adolescence, while the impact of genetic factors tends to increase during the transition to adulthood (Vrieze, McGue, & Iacono, 2012). It is important to note, however, that evidence for the role of common environment on substance abuse/dependence is still relatively limited and instead, largely supports its role in substance use (e.g. Fowler et al., 2007; Poelen et al., 2008; White, Hopper, Wearing, & Hill, 2003). Evidence from population-based transmission studies also suggests that common genetic factors contribute to the abuse of a broad range of illicit substances; and that these influences are of equal importance in men and women (Agrawal & Lynskey, 2008). Since all addictive be- haviors exert their rewarding effects by increasing dopamine (DA) in the striatum – a central structure in the mesocorticolimbic brain reward pathway – genetic variations affecting the DA system have been a major target for investigating vulnerability to drug abuse (Le Foll, Gallo, Le Strat, Lu, & Gorwood, 2009). It is clear, however, that the relationships between genetic factors on the one hand, and adverse drug-related be- haviors on the other, are complex and almost certainly not direct (Volkow & Muenke, 2012). Instead, genetic effects are mediated through many developmental processes including individual differences in per- sonality – for instance, a preference for immediately available rewards – and their interaction with equally powerful environmental factors such as exposure to addictive behaviors (Gorwood et al., 2012). Moreover, it is especially difficult to establish causal associations between genetic variation and addiction disorders because they typically develop over a period of time. Therefore, the factors that contribute to initial engage- ment in the behavior may be quite different from those contributing to its compulsive use and treatment resistance (Dawe & Loxton, 2004). 1.1. Addictive personality For decades, and across a variety of disciplines, the concept of an ‘addictive personality’ has been discussed and debated (e.g. Berglund et al., 2011; Eysenck, 1997; Lester & Narkunski, 1978; Nathan, 1988; Addictive Behaviors 38 (2013) 2306–2312 ⁎ Corresponding author at: 343 Bethune College, York University, 4700 Keele Street, Toronto, ON, M3J 1P3. Tel.: +1 416 736 2100x77327; fax: +1 416 923 3067. E-mail address: cdavis@yorku.ca (C. Davis). 0306-4603/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.addbeh.2013.02.012 Contents lists available at SciVerse ScienceDirect Addictive Behaviors