Most smokeless tobacco use does not cause cigarette smoking: Results from the 2000 National Household Survey on Drug Abuse

Those who either never progress from smokeless tobacco (SLT) to smoking or smoked before using SLT logically cannot have smoking caused by SLT use. The prevalence of such use permits strong inferences about the overall importance of the potential causal effects of SLT on cigarette smoking. We found that the majority of SLT ever users (66%) in the 2000 National Household Survey on Drug Abuse (NHSDA) were noncausal users. For these individuals, SLT use cannot have caused them to smoke. We also compared our results in 2000 with a similar sample in 1987, using current SLT users only. Potentially, the causal uses of SLT were in the minority and had not increased significantly over time (24% in 1987 to 29% in 2000, P>.05). Logistic models showed that, when noncausal users were removed, SLT was a minor predictor of current smoking. This is likely due to linked experimentation. We argue that that the majority of SLT use cannot cause smoking, such that SLT effects on smoking initiation are minimal at best. Policy implications of these findings are discussed.