Nicotine use and nicotine dependence (or tobacco use disorder) are influenced by both genetic liability and environmental factors (Le Foll et al., 2022; MAES et al., 2004). Several different smoking-related phenotypes have been studied, including smoking initiation (SmkInit) (Saunders et al., 2022), cigarettes per day (CPD) (Saunders et al., 2022), the Fagerström Test for Nicotine Dependence (FTND) (Quach et al., 2020), problematic tobacco use (PTU) (Hatoum et al., 2022), tobacco use disorder defined by codes from the International Classification of Diseases (ICD-based tobacco use disorder [ICD-TUD]) (Toikumo et al., 2024, and nicotine dependence (Loukola et al., 2014) defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-NicDep) (Table 1).Table 1.Definitions of different smoking-related phenotypes discussed in this article, the acronyms used to represent them, and the relevant GWASs used in analysesSmoking phenotypeShorthand name used in current manuscriptPhenotype definitionRelevant GWAS PubMed IDSmoking initiationSmkInitWhether someone has ever been a regular smoker.36477530Cigarettes per dayCPDNumber of cigarettes smoked per day.36477530Fagerström Test for Nicotine DependenceFTNDA six-item questionnaire assessing quantity of cigarettes smoked and compulsion to use, resulting in an ordinal measure of nicotine dependence.33144568Tobacco
