LCA results can shed light on two underlying patterns of data. Either underlying selleck kinase inhibitor all nicotine dependence criteria is a common unifying dimension (e.g., smoking quantity) or sets of criteria are etiologically distinct and oblique to each other resulting in subtypes of individuals. In the first instance, where endorsement of a set of criteria largely indexes a severity continuum, plotting the endorsement probabilities (as done in Figure 1) would result in a series of lines that are largely parallel to each other but have varying positions (i.e., index severity) along the y-axis. On the other hand, if distinct subtypes are identified, these lines would be expected to intersect, such that one class of individuals would be characterized by high endorsement probability on a series of criteria, while another class would show low endorsement probabilities for those criteria with a corresponding increase in endorsement probability for another set of criteria.

In our sample of regular smokers, four groups of individuals were identified��those with low endorsement of all criteria, those with high endorsement of all criteria, those with intermediate endorsement of FTND and DSM-IV, with particularly high levels of tolerance, and a class of individuals with intermediate endorsement of FTND criteria but only modest endorsement of DSM-IV�Cbased dependence criteria. Thus, while our findings primarily reflect a severity continuum (high endorsement vs. low endorsement of all criteria��in Figure 1, the lines denoting the HDHF, MDMF, and LDLF classes are nearly parallel), there is possible and suggestive support for a subgroup (LSMF class) of smokers.

This latter grouping is demonstrated by the intersection of endorsement probabilities for the DSM-IV tolerance criterion across the MDMF and LSMF classes (with a corresponding reversal of endorsement probabilities for some of the FTND criteria across these classes (e.g., higher endorsement of hate to give up first cigarette in the LSMF class). The MDMF class may be viewed as an intermediate risk class, and while the LSMF class appears to index similar vulnerability to the MDMF class, it is distinguished by a contrasting low endorsement of tolerance and a corresponding high endorsement of smoking less than 20 CPD. Furthermore, examination of the psychiatric covariates that aggregate with the classes highlights two key observations.

First, compared with those in the LDLF class, those in the LSMF class are more likely to be male, initiate smoking prior to age AV-951 13, report greater DSM-IV and FTND symptoms, report craving, and meet criteria for a lifetime history of DSM-IV conduct disorder and ADHD problems. Thus, while these individuals are lighter smokers, they demonstrate increased vulnerability to some psychopathology. Second, despite this increased risk, relative to those in the HDHF and MDMF class, the individuals in the LSMF class report the same levels of, if not significantly less, psychopathology.