Cross-tabulations were used to estimate the prevalence of SROs that occurred between the two surveys. Multivariate logistic regression analysis41 was used to estimate associations of baseline smoking with the subsequent onset and persistence of SROs, with and without controls for other baseline risk factors. In order to distinguish effects in predicting suicide ideation from effects on rarer SROs that are contingent on ideation, separate equations were used to predict ideation in the total sample and then, within the subsample of ideators, to predict conditional risk of plans, gestures, and attempts. A Tobacco Supplement dummy variable (DTS) was included in the prediction equations to distinguish panel survey respondents who were in the Tobacco Supplement from other respondents. Both types of respondents were included in the initial analyses, where the baseline smoking data were treated as equivalent in both subsamples even though these data were obtained retrospectively from panel sample respondents who did not participate in the NCS Tobacco Supplement. Once final models were developed, these models were expanded to include interactions between the smoking predictors and the DTS dummy variable in
