After a minimum of 2 days following completion of these procedures, all participants then participated in an abstinence incentive test during which abstinence from smoking was reinforced with money (see below for details). Procedures this Screening and Assessment Participants were recruited via flyers and advertisements and completed an initial telephone screen to determine interest and eligibility. Participants were then invited to complete an in-person screening session during which informed consent was obtained and further eligibility was determined. During the in-person screen, breath and urine samples were used to assess blood alcohol level and illicit drug use, respectively. CO was assessed with two breath samples: one upon arrival and the other after participants were allowed to smoke a cigarette.
In order to prevent exclusion of participants who may not have smoked recently prior to entering the laboratory, the minimum CO inclusion criterion was satisfied if either CO sample was greater than 8 ppm (All but four participants met criteria with the first breath sample). Participants then completed a battery of computer-administered questionnaires assessing demographic information, medical and psychiatric history, nicotine use history, and nicotine dependence. Following determination of eligibility, an assessment battery was administered, including additional measures of nicotine dependence, cigarette craving, and withdrawal. These scales have been thoroughly described elsewhere (FTND: Heatherton, Kozlowski, Frecker, & Fagerstr?m, 1991; NDSS: Shiffman, Waters, & Hickcox, 2004; WISDM: Piper et al.
, 2004; Minnesota Nicotine Withdrawal Scale [MNWS]: Hughes & Hatsukami, 1986). A four-item version of the Questionnaire on Smoking Urges (QSU-4: Carter & Tiffany, 2001) was administered during assessment only for Study 1. Abstinence Incentive Test The abstinence incentive test involved a series of brief daily visits to the laboratory during which abstinence from smoking was biochemically verified and reinforced with money according to a descending payment schedule. All participants were instructed to initiate abstinence on the Sunday following completion of initial procedures. Participants then attended daily sessions lasting approximately 15 min each on Monday through Friday, plus an additional visit the following Monday. During each visit, participants reported the number of cigarettes smoked over the previous 24 hr (or 72 hr on the last day) and completed computerized questionnaires assessing craving (QSU-4) and withdrawal (MNWS). Anacetrapib Breath CO samples were obtained daily to verify abstinence status. Participants were considered abstinent if they reported not smoking and had a CO reading of <6 ppm or a 50% reduction from the previous sample.