embedded. Based on prior work (Saccone et al., 2009b), we dichotomized FTND scores as follows: and FTND score ≥4 was defined as a “case”, an FTND score ≤1 was defined as a “control,” and subjects with scores in-between those values were considered to have an “unknown” phenotype. Most ND/FTND cases were diagnosed with alcohol dependence (AD), cocaine dependence (CD), and/or opioid dependence (OD) using the SSADDA instrument. The basic demographic information for participants in this study for the analysis of each of the smoking behaviors is summarized in Table 1.
