Smoking as a risk factor for suicide has been proposed by cohort studies that found a positive association between cigarette smoking and suicide or suicidal behaviors (Hemenway et al. 1993; Tverdal et al. 1993; Doll et al. 1994; Miller et al. 2000a; Miller et al. 2000b; Tanskanen et al. 2000; Breslau et al. 2005; Iwasaki et al. 2005; Yaworski et al. 2011). However, this relationship is controversial and the explanations for this association remain unclear (Hughes 2008). On the other hand, smoking cessation is often associated with a greater likelihood of experiencing withdrawal syndrome symptoms and depression, which might increase risk of suicide (Glassman et al. 1990; Laje et al. 2001). We therefore accessed data from three large U.S. cohorts in which cigarette smoking was assessed every two years to investigate prospectively and over a long follow-up period the association between smoking and quitting smoking and risk of deaths from suicide. The present work represents an extension of a previous brief report in the NHS (Hemenway et al. 1993) and a report based on only 8 years of follow-up in the HPFS (Miller et al. 2000b).
