To further explore whether the association between smoking and suicide remained after controlling for genetic and familial suicide risk factors, we investigated the relationship of smoking status with suicide in twin pairs discordant for both suicide and active smoking. Using a matched case–control design, we tested ORs using McNemar's test, and then we ran a pairwise survival model. Analyses were run in Stata/SE 12.1 (USA) on 9 July 2013.
