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Meta-Analysis
. 2016 Jul 8;11(7):e0156348.
doi: 10.1371/journal.pone.0156348. eCollection 2016.

Smoking and Suicide: A Meta-Analysis

Jalal Poorolajal  1 , Nahid Darvishi  2
Affiliations
Meta-Analysis

Smoking and Suicide: A Meta-Analysis

Jalal Poorolajal et al. PLoS One. .

Abstract

Background: Many studies have reported a positive association between smoking and suicide, but the results are inconsistent. This meta-analysis was carried out to estimate the association between smoking and suicidal ideation, suicide plan, suicide attempt, and suicide death.

Methods: Major electronic databases including PubMed, Web of Science, Scopus, and ScienceDirect were searched until May 2015. The reference lists of included studies were screened too. Epidemiological studies addressing the association between smoking and suicidal behaviors were enrolled. The heterogeneity across studies was explored by Q-test and I2 statistic. The possibility of publication bias was assessed using Begg's and Egger's tests and Trim & Fill analysis. The results were reported based on risk ratio (RR) and odds ratio (OR) with 95% confidence intervals (CI) using a random-effects model.

Results: We identified a total of 8062 references and included 63 studies with 8,063,634 participants. Compared to nonsmokers, the current smokers were at higher risk of suicidal ideation (OR = 2.05; 95% CI: 1.53, 2.58; 8 studies; I2 = 80.8%; P<0.001), suicide plan (OR = 2.36; 95% CI: 1.69, 3.02; 6 studies; I2 = 85.2%; P<0.001), suicide attempt (OR = 2.84; 95% CI: 1.49, 4.19; 5 studies; I2 = 89.6%; (P<0.001), and suicide death (RR = 1.83; 95% CI: 1.64, 2.02; 14 studies; I2 = 49.7%; P = 0.018).

Conclusions: There is sufficient evidence that smoking is associated with an increased risk of suicidal behaviors. Therefore, smoking is a contributing factor for suicide. Although this association does not imply causation, however, smoking prevention and cessation should be the target of suicide prevention programs.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Flow of information through the different phases of the systematic review.
Fig 2
Fig 2. The risk of suicide ideation among current smokers versus nonsmokers.
Squares and the horizontal lines represent the measures of effect, e.g. odds ratio or relative risk, and associated confidence intervals for each of the studies and the diamond indicates the summary measure.
Fig 3
Fig 3. The risk of suicide plan among current smokers versus nonsmokers.
Squares and the horizontal lines represent the measures of effect, e.g. odds ratio or relative risk, and associated confidence intervals for each of the studies and the diamond indicates the summary measure.
Fig 4
Fig 4. The risk of suicide attempt among current smokers versus nonsmokers.
Squares and the horizontal lines represent the measures of effect, e.g. odds ratio or relative risk, and associated confidence intervals for each of the studies and the diamond indicates the summary measure.
Fig 5
Fig 5. The risk of suicide death among current smokers versus nonsmokers.
Squares and the horizontal lines represent the measures of effect, e.g. odds ratio or relative risk, and associated confidence intervals for each of the studies and the diamond indicates the summary measure.
Fig 6
Fig 6. Trim and Fill analysis estimating the number possible missing studies for the association between smoking and suicide ideation.
The squares represent the possible missing studies.
See this image and copyright information in PMC

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