The time at which participants chose to smoke was the primary dependent variable (range 0�C50min), coded into 5-min intervals for analysis. Following the first cigarette (or the end of the delay period if smoking not initiated), CHIR99021 GSK-3 participants were provided a $4.00 ��tab,�� which they could save or use to smoke additional cigarettes at $0.50 each. Measures Severity of nicotine dependence was assessed using the Fagerstr?m Test for Nicotine Dependence (FTND; Heatherton et al., 1991). Nicotine withdrawal was assessed with the 7-item Minnesota Nicotine Withdrawal Scale (Hughes & Hatsukami, 1986). Responses ranged from 0 (none) to 4 (severe). Total score is the mean of the 7 items. Motivation to remain abstinent during the task was assessed indirectly with a single item that asked participants to rate on a 0 (not at all) to 10 (extremely) scale the importance of maximizing payments on study tasks.

BH (Brown et al., 2002; Hajek et al., 1987) was assessed at baseline with a stopwatch by asking participants to hold their breath for as long as they could. BH duration (seconds to exhalation) correlates positively with ability to tolerate exposure to CO2-enriched air (Brown et al., 2002, 2009), duration of maintaining a grip (Hajek, 1989; i.e., physical distress tolerance), a behavioral measure of frustration tolerance, and self-report measures of tolerance for both frustration and anxiety (McHugh & Otto, 2011). Self-reported smoking-specific DI was assessed at baseline with the Intolerance for Smoking Abstinence Discomfort Questionnaire (IDQ-S; Sirota et al.

, 2010), a psychometrically validated 17-item questionnaire. The IDQ-S has two subscales: Withdrawal Intolerance (e.g., ��I can��t stand that restless, jittery feeling I get if I go too long without a cigarette��) and Lack of Cognitive Coping (e.g., ��To get through a day without a cigarette, I think to myself ��no pain, no gain������reverse scored). Items are rated on a scale of 1 (strongly disagree) to 5 (strongly agree), with the scale scores being the mean of these items. Data Analysis Plan We first ran correlations among background baseline characteristics, BH, IDQ-S subscales, and nicotine withdrawal at the experimental session. We then ran Cox proportional hazards analyses to predict risk of initiating smoking. Models controlled for sex, FTND, experimental conditions, and the interaction between female gender and Told Alcohol.

Each measure of DI was entered individually as a predictor of initiating smoking along with severity of nicotine withdrawal symptoms at the start of the session and motivation to maximize payment. In the second step of these models, interactions between the DI measure and both withdrawal and motivation were added. RESULTS AV-951 Table 1 shows the means and correlations among key study variables. Women had significantly shorter BH duration than men. BH was positively associated with having ever had a 24-hr quit attempt but not with the FTND.