Our finding is the first robust association between a common genetic variant and smoking cessation. Previous candidate gene association studies investigating smoking cessation have used much smaller sample sizes and have either shown inconsistent results or require replication in independent larger studies (17,18). While our statistical evidence does not meet generally accepted criteria for ‘genome-wide significance’ (P < 5 × 10−8), the prior genome-wide association with smoking quantity (P = 6 × 10−20) (10), coupled with the strong evidence for association in our study (P = 0.0003–0.0006), suggests that our result is unlikely to be a false-positive.
