Moderate DSM-Moderate FTND This class (27% of participants, N = 167) is distinguished by moderate to high endorsement probability of the DSM-IV criteria of tolerance, larger/longer and time spent, and moderate kinase inhibitor Oligomycin A endorsement probability of the FTND criteria. Individuals in this class are most likely to endorse smoking 11�C25 CPD. These individuals are, therefore, likely to be moderate smokers with tolerance to nicotine and dependence problems indexed more distinctly by DSM-IV criteria. Light Smokers�CModerate FTND This class included 19% of the regular smokers (N = 117) and was distinguished by a very low endorsement probability for tolerance and moderate endorsement probabilities for the FTND criteria (smoking where not allowed, hate to give up first cigarette, smoking more within the first hour of waking, and smoking when ill in bed) as well as for the DSM-IV criteria of withdrawal, larger/longer, and quit/cut back.

Individuals in this class tended to be more likely to endorse smoking within 6�C60 min of waking but were less likely to be heavy smokers as indexed by higher endorsement of CPD = 1 (i.e., 11�C19 CPD). Hence, for ease of interpretation, we label this group as lighter smokers with moderate FTND (LSMF). Table 1 shows the prevalence of individual criteria for and diagnosis of DSM-IV�C and FTND-based nicotine dependence across the four classes. These post-hoc comparisons revealed that members of the low DSM-low FTND (LDLF) class had uniformly the lowest prevalence of DSM-IV and FTND criteria with only 5.5% meeting criteria for a DSM-IV diagnosis and none meeting criteria for FTND-based nicotine dependence.

In contrast, 57.1% and 100% of those in the high DSM-high FTND (HDHF) class met criteria for nicotine dependence via DSM-IV and FTND criteria, respectively. Interesting differences across the remaining two classes (moderate DSM-moderate FTND [MDMF] and LSMF) are underscored by the prevalence of criteria and diagnoses in Table 1. For instance, while approximately equal numbers of individuals in the MDMF class met criteria for an ND diagnosis using DSM-IV and/or FTND (44%�C46%), the prevalence of FTND-based ND (51%) exceeded DSM-IV ND (18%) in the LSMF class. While DSM-IV ND was more common in the MDMF versus LSMF class, the prevalence of FTND-based ND could be equated across these two classes.

Also, all members of the MDMF class but only 4% of those in the MDMF class reported tolerance. In contrast, 10% of the members in the LSMF class reported giving up activities to smoke, while only 3% of those in the MDMF class reported it. Variations in FTND criterion endorsement across these classes were also pronounced with members of the LSMF class, overall, endorsing significantly more FTND items than those in the MDMF class (e.g., 23% of LSMF members endorsed smoking within the first Entinostat hour of waking, while only 1.