This association was inhibitor MG132 lost, however, after controlling for lifetime alcohol use disorders. Increased risk for ST use among those with PTSD but not major depression is generally consistent with previous studies (Goodwin et al., 2008). No significant associations emerged from the regression analyses with the Southwest tribe, underscoring the complexity of studying these relationships both within and across tribes. Psychiatric comorbidity showed a significant trend-level increase in the odds of ST use among both tribes. However, the rates were modest and actually peaked at two disorders before declining when three or more psychiatric disorders were present. Future research may wish to assess other cultural, demographic, biological, health, familial, and social factors that may mediate and moderate any latent association between psychiatric disorders and ST use among American Indians.

This study has several limitations. First, our operationalization of lifetime ST use was liberal which could have inflated our prevalence rates. Considerable variability is evident with how ST use has been surveyed, making comparisons with other samples challenging. For example, some studies have assessed ST based on ever using chewing tobacco or snuff at least 20 times in their lifetime (Centers for Disease Control and Prevention, 2006; Goodwin et al., 2008; Nelson et al., 2006; Redwood et al., 2010). Data from the Current Population Survey (Mumford, Levy, Gitchell, & Blackman, 2006) and the National Health Survey (Nelson et al., 2006) even showed changes in the wording of the lifetime ST use questions across repeated sampling periods.

Our study also assessed only chewing tobacco use, whereas other studies have asked about both chewing tobacco and snuff together (Redwood et al., 2010) or chewing tobacco and snuff separately (Nelson et al., 2006). Differences in how tobacco use questions have been asked are also apparent in the cigarette smoking literature (Ziedonis et al., 2008). Second, we did not assess how much or how frequently tribal members used ST in their lifetime. A more refined measurement of both the quantity and frequency of ST could help determine if a dose-dependent relationship exists with psychiatric disorder status or if nicotine dependence is more strongly related to anxiety and depressive disorders.

Defining cigarette smoking in terms of pack-years has been an accepted method of assessing cumulative exposure to tobacco use. Such a shared metric for lifetime ST is not readily available. Measuring quantity and frequency of ST use would provide a more accurate assessment of exposure risk than the generic ��ever use�� construct (Bell et al., 2009). Third, data from the AI-SUPERPFP were collected between 1997 and 1999, and therefore, trends in ST use among the tribes GSK-3 may have changed over time. Fourth, our cross-sectional design does not permit inferences about the direction of the associations.