Aims
Nicotine dependence is a highly heritable disorder associated with severe medical morbidity and mortality. Recent meta‐analyses have found novel genetic loci associated with cigarettes per day (CPD), a proxy for nicotine dependence. The aim of this paper is to evaluate the importance of phenotype definition (i.e. CPD versus Fagerström Test for Cigarette Dependence (FTCD) score as a measure of nicotine dependence) on genome‐wide association studies of nicotine dependence.
Design
Genome‐wide association study.
Setting
Community sample.
Participants
A total of 3365 subjects who had smoked at least one cigarette were selected from the Study of Addiction: Genetics and Environment (SAGE). Of the participants, 2267 were European Americans, 999 were African Americans.
Measurements
Nicotine dependence defined by FTCD score ≥4, CPD.
Findings
The genetic locus most strongly associated with nicotine dependence was rs1451240 on chromosome 8 in the region of CHRNB3 [odds ratio (OR) = 0.65, P = 2.4 × 10−8]. This association was further strengthened in a meta‐analysis with a previously published data set (combined P = 6.7 × 10−16, total n = 4200). When CPD was used as an alternate phenotype, the association no longer reached genome‐wide significance (β = −0.08, P = 0.0004).
Conclusions
Daily cigarette consumption and the Fagerstrom Test for Cigarette Dependence show different associations with polymorphisms in genetic loci.