Psychological Medicine

Original Articles

Cigarette smoking and suicidal behaviour: results from a 25-year longitudinal study

J. M. Bodena1 c1, D. M. Fergussona1 and L. J. Horwooda1

a1 Christchurch Health and Development Study, University of Otago, Christchurch, Christchurch, New Zealand

Abstract

Background This study examined the associations between cigarette smoking and suicidal ideation and suicide attempts, both before and after control for potentially confounding using fixed effects regression models.

Method Data were gathered during the Christchurch Health and Development Study, a 25-year longitudinal study of a birth cohort of New Zealand children (635 males, 630 females). The analysis was based on a sample of 1041 participants with available data on cigarette smoking and suicidal behaviour from ages 16 to 25 years. The main outcome measures were suicidal ideation and suicide attempts, ages 16–18, 18–21, and 21–25.

Results There were significant bivariate associations between the frequency of cigarette smoking and both suicidal ideation and suicide attempts. Cohort members who smoked 20 or more cigarettes per day had odds of suicidal ideation that were 3.39 times (95% CI 2.06–5.59) those of non-smokers, and odds of suicide attempt that were 4.39 (95% CI 2.18–8.85) times those of non-smokers. Control for non-observed fixed confounding factors reduced the association between cigarette smoking and suicidal ideation and suicide attempts to statistical non-significance. After adjustment, those smoking more than 20 cigarettes per day had odds of suicidal ideation that were 1.00 times (95% CI 0.46–2.18) those of non-smokers, and odds of suicide attempt that were 1.84 (95% CI 0.81–4.18) times those of non-smokers.

Conclusions The findings suggest that the associations between frequency of cigarette smoking and suicidal behaviour may largely be explained by the non-observed background factors and life circumstances that are associated with both cigarette smoking and suicidal behaviour.

(Received December 04 2006)

(Revised July 05 2007)

(Accepted July 12 2007)

(Online publication September 25 2007)

Correspondence

c1 Address for correspondence: Dr J. M. Boden, Christchurch Health and Development Study, Christchurch School of Medicine and Health Sciences, PO Box 4345, Christchurch, New Zealand. (Email: joseph.boden@otago.ac.nz)

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