Four methodological limitations need to be noted in evaluating the substantive meaning our results. First, our predictors are limited by the fact that no information was collected about smokeless tobacco use or about quantity-frequency of smoking (e.g., number of cigarettes, cigars, or pipes smoked per day; number of years smoked). The prospective associations found here might have been stronger if the predictors had included these refinements. Second, we did not consider the possibility that some people who make suicide plans and attempts might deny ever having suicide ideation, as the skip logic used in our surveys only assessed plans and attempts among respondents who reported a history of suicide ideation. Third, we did not control for all DSM-IV disorders. Non-affective psychosis (NAP), for example, was not included in the core NCS-R assessment. Yet we know that both smoking44 and suicidality45 are comparatively common among people with NAP. Exclusion of NAP, then, presumably led to an overestimation of the net effects of smoking. Fourth, although control data on history of pre-existing mental disorders and suicidality were gathered prospectively in our two-wave
