, 2000). The cessation outcomes of the parent study will therefore fill an important gap in the literature about effects of evidence-based cessation interventions in a population of homeless smokers with high nicotine dependence. This study also showed that in this sample http://www.selleckchem.com/products/Bortezomib.html of smokers, there were high rates of comorbidities with depression, alcohol, and other substance abuse with nearly 40% having PHQ-9 scores in the moderate or worse depression range and nearly half considering themselves as being alcoholic or chemical dependent. Studies (Humfleet, Munoz, Sees, Reus, & Hall, 1999; Sullivan & Covey, 2002; Torchalla et al., 2011) in other populations have shown that these comorbidities make quitting smoking more challenging. However, there are currently no data about the effects of these comorbidities on smoking cessation in homeless populations.

Unlike the typical protocol of smoking cessation studies in the general population that excludes smokers with these comorbid conditions, smokers with these conditions were allowed to enroll in this study, provided they were medically stable as determined by a psychiatrist. This protocol decision was made to ensure that the study sample would be similar to homeless smokers in general, which would enhance the study��s external validity. Findings from the final outcomes of this trial will provide guidance regarding addressing these comorbidities in the context of smoking cessation interventions. This study has some limitations.

First, the study was conducted at a single metropolitan area in the upper Midwest of the United States, and there may be differences between cities, states, or regions within a country and between countries that could affect sociodemographic characteristics of homeless persons enrolled in a smoking cessation study. However, several demographic and substance use characteristics of study participants are comparable with those of homeless populations in other areas (Wilder Foundation, 2009). Second, because this study was a treatment study, the sample was self-selected and motivated to quit smoking and thus may not be representative of homeless smokers generally. The high motivation of participants may also make MI less effective since MI is best suited for less motivated people. However, the study was designed with minimal exclusion criteria so that the external validity of findings would be enhanced.

Given the high motivation for smoking cessation among homeless smokers, future studies should consider either enrolling only less motivated smokers for whom MI would be better suited or utilized a different counseling technique such as cognitive behavioral therapy. However, the decision to enroll a more ��selective�� population should be weighed with the potential ethical GSK-3 implications of excluding motivated smokers in a population already disenfranchised from clinical research.