Whereas a strength of this study is its strong control for potential confounders, the primary limitation is the possibility of incomplete ascertainment of potentially confounding factors related to both smoking and suicide. We assessed contributions of indicators of diagnosed and undiagnosed psychiatric morbidity at two time points with the LSS as a proxy for pre-existing depressiveness, excess daily and binge alcohol use, sedative–hypnotic use, unemployment, marital status, and other demographic characteristics. We cannot rule out entirely the possibility that these factors changed differentially in smokers v. non-smokers over the 35-year follow-up period; however, data from subsets of the cohort presented in this paper were available on questionnaire-based measures between 1975/1981 and 2011. Analyses of differential stability of these risk factors from 1975/1981 to 2011 in smokers v. never smokers did not reveal substantial change over time in these self-report measures by smoking status. We additionally assessed contribution of and removed from analyses those with psychiatric disability and antipsychotic and antidepressant medication use over the 35-year follow-up. For this purpose, we considered treatment for psychiatric illness as an indicator for diagnosed
