We then repeated these analyses, using the Log-rank test and stratifying by those who had or had not smoked 100 cigarettes Wortmannin by the end of the follow-up assessment. Finally, logistic regression models were used to examine whether nicotine dependence (both the NDSS total score and endorsement of individual symptoms) predicted daily smoking at the 48-month follow-up, controlling for previous highest level of smoking frequency (days smoked in past 30 days drawn from each assessment), highest smoking quantity (number of cigarettes smoked in past week at each assessment), gender, ethnicity (White vs. non-White), and age of smoking initiation. Participants with missing data were excluded from the logistic regression analysis. The missing data were primarily caused by the attrition of participants during the 4-year follow-up period.

In the present study, smoking behavior at the 4-year follow-up could not be determined for 17 of 169 participants. Results Figure 1 illustrates the cumulative probability of each nicotine dependence symptom according to time since smoking initiation. Escalation of the cumulative probability was particularly rapid for reports of ��increase in the amount smoked,�� ��smoking to relieve restlessness and irritability,�� and ��smoking a lot more now to be satisfied compared to when first smoked,�� with substantially slower increases in the cumulative probability of ��better functioning in the morning after having a cigarette,�� ��buying cigarettes instead of lunch,�� and ��willingness to go outside in a rainstorm to get cigarettes.

�� Overall, the cumulative increases of individual nicotine dependence symptoms were fairly stable across time. Figure 1. Cumulative probability of developing dependence symptoms following smoking initiation. Satisfaction = smoking a lot more now to be satisfied compared with when first smoked; Increase = increase in the amount smoked; Relieve = smoking to relieve restlessness … Figure 2 illustrates the number of months after smoking initiation when the cumulative probability of developing each symptom was 25%. The 95% CIs are based on Kaplan�CMeier survival analyses. The symptom ��increase in the amount smoked�� was reported by 25% of smokers within 1 year of initiation, whereas ��smoking a lot more now Cilengitide to be satisfied compared to when first smoked�� and ��smoking to relieve restlessness and irritability�� were reported by 25% of smokers within 2 years of initiation. Compared with other individual symptoms, the symptom of ��better functioning in the morning after having a cigarette�� developed more slowly, taking 4 years to reach a cumulative probability of 25%. Figure 2.