Several previous prospective epidemiological studies found, unlike us, that significant gross prospective associations between smoking and SROs disappeared entirely after controlling for a series of risk factors.15, 17, 18 The fact that we found at least one of these associations to remain, between the highest level of smoking involvement and subsequent suicide plans, might be due to the fact that the smoking variables in these earlier studies all measured use rather than nicotine dependence, whereas the significant net association in our study involved early-onset nicotine dependence. Another possible explanation for the difference between our result and the results of these earlier studies is that our finding of a significant net association is a chance finding due to the fact that we examined associations between many different measures of smoking and four different measures of SROs. Replication of our finding that early-onset nicotine dependence predicts suicide plans among ideators is needed before we can reject the hypothesis of chance association. It is also noteworthy that one other previous prospective epidemiological study found more consistent evidence than we did of statistically significant
