We investigated for an association between 15q25.1, 5p15.33 and 6p21.33 variants and smoking behaviour by studying the relationship with consumption of cigarettes per day (CPD) categorised into different levels of smoking quantity (Table 3). A strong relationship between all 15q25.1 variants (rs12914385, rs8042374 and rs938682) and smoking was observed (Table 3). Statistically significant allele-dependent associations between risk genotype and cigarette consumption was seen in cases. A similar trend was observed in controls for each of the SNPs but was not statistically significant. Adjusting rs8042374 or rs938682 for rs12914385 provided evidence of an independent effect of the two loci on smoking behaviour (P <0.05). No significant association was observed between 5p15.33 (rs4975616, rs2736100) and 6p21.33 (rs3117582) genotypes and smoking.
