Other than the present one, there have been seven longitudinal epidemiological studies of smoking and SRO.14–20 The positive effect of current smoking on future SRO reported here was also observed in three studies.14–16 Problems of recall due to the long 10-year interval between data time points could explain the negative finding of the study by Kessler et al17; while the younger age of the samples in two studies19 20 could have masked a future effect. Of clinical and public health importance is the finding, first reported here, that longer abstinence from smoking decreased the risk for SRO. The latter observation, not considered in two negative studies regarding past smoking,14 16 could account for the inconsistent findings. Notably, the divergence according to longevity of abstinence is consistent with evidence for lung cancer and other smoking-related disorders that risk reduction from stopping smoking occurs only after multiple years of abstinence.30 31 The worrisome observation that relapsers and new smokers are at even higher risk of future SRO than persistent smokers suggests particular targets for increased therapeutic attention. Finally, the data negated a
