Regular daily smoking among 14-year-old adolescents increases the subsequent risk for suicide: the Northern Finland 1966 Birth Cohort Study.

OBJECTIVE: To investigate the relationship between adolescent regular daily smoking and later suicides in a prospective longitudinal birth cohort setting.
METHOD: Data from the Northern Finland 1966 Birth Cohort Study (N = 10,934) were linked with national death certificates from Statistics Finland. The information on suicide attempts until the end of 2001 was gathered from the Finnish Hospital Discharge Register (FHDR). The information on adolescent regular daily smoking was gathered via a questionnaire in 1980 and 1981, when the subjects were age 14 years.
RESULTS: Of all cohort males who smoked regularly at age 14 years, 2.6% committed suicide by age 34 years, while the corresponding proportion was 0.8% among experimental smokers and 0.4% among non-smokers (chi2 = 15.8, df = 2, p < .001). After adjusting for sociodemographic factors in adolescence and psychiatric morbidity, regular smokers were at a 4.05-fold hazard (95% CI = 1.18 to 13.93, p = .026) for committing suicide at a younger age. Corresponding associations were not found among females. The choice of suicide method was not associated with smoking habits in adolescence. Furthermore, the proportion of suicide attempts was significantly higher among regular daily smokers, among both boys (3.3% vs. 1.2%) and girls (4.2% vs. 1.2%), compared with other adolescents.
CONCLUSION: At the epidemiologic level, adolescent regular smoking was found to be associated with increased risk for suicide among males before the age of 34 years. Further studies are needed to investigate the effects of smoking on neurobiology of depression, self-damaging aggression, and impulsive behavior.