Association of serotonin transporter gene polymorphism with nicotine dependence: no evidence for an interaction with trait neuroticism

We sought to replicate previous studies reporting a moderating effect of the 5HTT gene on the association between trait neuroticism and smoking behaviour, and extend on this work by including a formal test of this interaction, in a sample of 141 heavy smokers. Nicotine dependence was measured using the Fagerström Test for Nicotine Dependence; trait neuroticism was assessed using the Eysenck Personality Questionnaire. All participants were genotyped for the 5HTT-LPR polymorphism. A 3 · 2 ANOVA of nicotine dependence score, with genotype (L/L, L/S, S/S) and neuroticism (high, low) as between-subjects factors, indicated a significant main effect of genotype (F[2, 135] = 3.13, p < 0.05) in the predicted direction, with the short allele of the 5HTT gene being associated with higher nicotine dependence score. There was a marginal effect of neuroticism (F[1, 135] = 3.01, p = 0.08) in the predicted direction, with high trait neuroticism being associated with higher nicotine dependence score. The interaction effect was non-significant (F < 1). These data suggest that 5HTT genotype is associated with nicotine dependence independently of any association between this gene and trait neuroticism that may modulate smoking behaviour. We failed to 0191-8869/$ see front matter 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.paid.2004.06.008 * Corresponding author. Tel.: +44 1865 224807; fax: +44 1865 224989. E-mail address: [email protected] (M.R. Munafò). www.elsevier.com/locate/paid Personality and Individual Differences 38 (2005) 843–850 replicate the finding of a moderating influence of 5HTT genotype on the association between neuroticism and nicotine dependence. 2004 Elsevier Ltd. All rights reserved.