Genome-wide association studies (GWAS) of nicotine use behaviors have largely focused on phenotypes that are easily ascertained through self-report questionnaires (e.g., when did you start smoking?, are you a current smoker?, and how many cigarettes do you smoke in a day?). The largest genome-wide association studies (GWAS) of tobacco smoking behaviors to date identified 140 loci associated with cigarettes per day (CPD; N = 784,353)3.
