To evaluate the impact of additional potential confounding factors, in cohorts that did and did not exclude those with co-morbid psychiatric and medical conditions as defined above, we ran models with smoking status in 1975, sex and one additional variable to see whether inclusion of the variable influenced the association between smoking status in 1975 and suicide to 2011. We considered a decrease of 5% or more in the HR for suicide (HR 2.59 for active smokers, see Table 2) to be sufficiently large for the variable to be retained for additional analyses. When added to the model, neither socio-economic variables nor employment status substantially affected the association of smoking on suicide.
