The most statistically significant SNPs, namely CHRNA3-rs1051730 and TTC12-rs10502172, were selected for further analyses. Main effects of CHRNA3-rs1051730 and TTC12-rs10502172 on smoking behaviours were tested using multinomial-logistic regression run in SAS v9.2. Smoking at 14 and 31 years were coded using three categories (age 14: regular/occasional/non-smokers; age 31: heavy/light/non-smokers) with non-smokers being the reference category.
