To identify additional genetic loci, we conducted the largest GWAS meta-analysis for nicotine dependence to date. We used the Fagerström Test for Nicotine Dependence (FTND), a six-item questionnaire with scores that range from 0 to 10 and indicate the level of physiological dependence on nicotine.10, 11 The FTND focuses on the core criteria for dependence, including heavy use/tolerance (for example, CPD) and withdrawal (for example, time to first cigarette in the morning), and although it does not capture some factors such as craving, the FTND remains the strongest predictor of smoking cessation among the primary measures of nicotine dependence.12 It has also been shown to provide a robust measure of nicotine dependence across different settings and populations.13
