Participants were recruited from the Collaborative Genetic Study of Nicotine Dependence (COGEND), a multi-site project in the United States [1]. Potential subjects were excluded from participation if they reported regularly using psychotropic medications (e.g., paroxetine, fluoxetine, nortriptyline, sertraline, heloperidol, olanzepine, risperidone, quetiapine, diazepam, valproate, lithium), systemic steroids, antihistamines, or cimitidene. Oral contraceptive use was not determined. All subjects were self-identified as being of European ancestry and between 27 and 44 years of age. Self-reported race was previously verified using EIGENSTRAT [2]. Current smoking status was defined by a mean non-deuterated cotinine measurement of >2 ng/ml. The relatively low cut-point was chosen to exclude all individuals who reported smoking in the previous week. One male subject currently using a nicotine patch was excluded from all analyses of smoking status. Results for all analyses of smoking status did not differ using a more stringent definition (mean D0-cotinine > 20 ng/ml). Subject characteristics are summarized in Supplemental Table 1. All subjects were requested not to consume food, and especially grapefruit and grapefruit juice, for 12h prior to their visit. Subjects were not asked
