95% CI 2.31–5.22) than daily smokers who smoked less (HR 2.3, 95% CI 1.61–3.23) (p = 0.017, test of homogeneity of regression coefficients), with never smokers as overall reference (HR 1). Age of smoking initiation among active smokers, i.e. initiation before age 18 years compared with initiating later, was not associated with suicide risk (data not shown). Both non-daily and daily smokers had elevated risk of subsequent suicide over never smokers that did not differ significantly from each other when modeled separately (HR 2.44, 95% CI 1.29–4.62, and HR 2.60, 95% CI 1.87–3.62, respectively) (not shown in Table 2). Active smokers had a higher cumulative suicide incidence than never smokers at every age (except the oldest age group where the HR point estimate is high but the sample size is small, limiting power to detect an effect) (Table 2, Fig. 1). Active male smokers had the highest suicide risk (70/100 000 person-years), and never-smoking women the lowest (7.3/100 000 person-years). Those who had quit smoking did not have elevated suicide risk, though HR point estimates were greater than unity (Table 2). Table 2.Risk among former and active smokers in 1975 compared with never smokers for suicide in the Finnish Twin
