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.
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.
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).
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.
Citation: Poorolajal J, Darvishi N (2016) Smoking and Suicide: A Meta-Analysis. PLoS ONE 11(7): e0156348. https://doi.org/10.1371/journal.pone.0156348
Editor: Osama Ali Abulseoud, National Institute on Drug Abuse, UNITED STATES
Received: January 24, 2016; Accepted: May 10, 2016; Published: July 8, 2016
Copyright: © 2016 Poorolajal, Darvishi. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information files.
Funding: The authors would like to thank the Vice-chancellor of Research and Technology, Hamadan University of Medical Sciences, for financial support of this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Each suicide is a tragedy. Every 40 seconds a person dies from suicide somewhere in the world. The estimated global burden of suicide is over 800,000 deaths per year . Suicide accounted for 1.4% of total mortality and 15% of injury mortality of the world in 2012 . These figures underestimate the problem. For each suicide related death, there are approximately 10 to 40 attempted suicides . In addition, a lot of people with suicidal thoughts never seek services . Suicides occur in all parts of the world and throughout the lifespan. It is the second leading cause of death in young people 15 to 29 years of age and is highest in persons aged 70 years or over for both men and women in most regions of the world . Suicide is one of the greatest sources of premature death .
There is no single cause or stressor for suicide, but numerous psychological, social, biological, and cultural factors contribute to suicide [6–8]. Psychological disorders as well as alcohol and substance abuse disorders are among the major contributing factors for suicide [9–11]. Several epidemiological studies have reported an association between smoking and suicidal behaviors, but the results are inconsistent. A meta-analysis was conducted by Li et al  to estimate the overall association between smoking and suicide related death based on the studies published by May 2011. However, the association between smoking and other suicidal behaviors, such as suicidal ideation, suicide plan, and suicide attempt was not addressed. Furthermore, so far, several epidemiological studies have recently been conducted to address the relationship between smoking and suicidal behaviors. Therefore, an update and comprehensive meta-analysis is needed. We performed this meta-analysis based on current evidence to estimate the association between smoking and suicidal behaviors, including suicidal ideation, suicide plan, suicide attempt, and suicide death.
Materials and Methods
Protocol and registration
This review was approved and funded by the Vice-chancellor of Research and Technology, Hamadan University of Medical Sciences. This report was prepared according to the PRISMA, an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses . The supporting PRISMA checklist of this review is available as supporting information; see S1 PRISMA Checklist. The protocol was registered with the Prospero—Center for Reviews and Dissemination on 2 June 2015 (CRD42015022054), available from: http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42015022054
The exposure of interest was smoking. Based on smoking habits, the participants were classified as non-smokers (never smoked or smoked less than 100 cigarettes), ex-smokers (smoked at least 100 cigarettes, but did not smoke in the past 30 days), or current smokers (smoked at least 100 cigarettes and smoked in the past 30 days . We included the studies that reported cigarette habits, according to these categories or at least compatible with them. We excluded studies that did not distinguish between current smokers and former smokers (so called ever smokers), or assessed the association between suicide and age of initiation of smoking rather than a smoking habit itself, or compared the risk of suicide in high smokers versus low smokers, see S1 Excluded Studies With Reasons.
The outcome of interest was suicide. Suicidal behaviors were classified as suicidal ideation (seriously thought about committing suicide during past 12 months or life time), suicide plan (making a plan for committing suicide during the past 12 months or lifetime), suicide attempt (actually attempting suicide during the past 12 months or lifetime), and suicide death (dying of suicide) .
Observational studies, such as cohort, case-control, and cross-sectional studies, investigating the association between smoking and suicidal behaviors in general population were enrolled irrespective of language, date of publication, nationality, race, age, and gender. We excluded studies that did not discriminate among different types of suicidal behaviors or assessed the association between suicide and smoking in people with mental disorders.
Information sources and search
Major electronic databases, including PubMed, Web of Science, Scopus, and ScienceDirect were searched until May 2015. The reference lists of the included studies were searched to identify additional studies.
The following search terms were used individually and in combination: (suicid* or self-injurious behavior or self-mutilation or self-immolation or self-harm or self-inflicted or self-injury or self-slaughter or self-destruction) and (smoking or tobacco or cigarette or cigar).
We combined search results from different databases using EndNote reference manager software and deleted duplicate records of the same report. Then, two authors screened independently titles and abstracts to remove ineligible studies. Disagreements were resolved by discussion. We retrieved the full text of the potentially eligible studies and examined full-text reports for further evaluation. In cases where there were multiple reports of the same study, we used the last published report.
We extracted data from relevant studies using an electronic data collection form prepared in Stata software. We contacted study authors, where appropriate, to request further information, such as missing results. We extracted the following information: first author’s name, year of publication, country, language, population type (general population, conscripts/veterans), age of participants, gender, design of the studies (cohort, case-control, cross-sectional), suicidal behaviors (ideation, plan, attempt, completed), effect estimate (risk ratio, odds ratio), sample size, effect sizes and related 95% confidence intervals (CIs).
The methodological quality of the included studies was examined using Newcastle Ottawa Statement (NOS) Manual . The NOS is a practical scale for assessing the quality of observational studies with their design and content. This scale includes a set of items and allocates a maximum of nine stars to the following domains: selection, comparability, exposure, and outcome. In this meta-analysis, the studies with six star-items or less were considered low-quality and those with seven star-items or more were considered high-quality.
Heterogeneity and reporting biases
Heterogeneity was examined by chi-squared test  and its quantity was measured by the I2 statistic . The possibility of publication bias was investigated by the Egger's  and Begg's  tests and Trim and Fill method .
We used the risk ratio (RR) and the odds ratio (OR) with their 95% confidence intervals (CI) to express the association between smoking and suicidal behaviors. We analyzed data and reported the results based on a random-effects model . We performed statistical analyses at a significance level of 0.05 using Stata software, version 11 (StataCorp, College Station, TX, USA).
We performed subgroup analysis according to the quality of included studies (high-quality and low-quality).
In cases the between-study heterogeneity was high, we evaluated the source of heterogeneity using sequential algorithm . According to this algorithm, one study was excluded from the calculations each time. The study that was responsible for the largest decrease in I2 was dropped. This process was repeated for a new set of n-1 studies. We continued by successively reanalyzing reduced sets of studies until I2 dropped below the intended threshold 50%. When there was a chance more than one omitted studies could result in I2 dropping below the desired threshold, we reported the minimum I2.
Description of studies
We identified a total of 8062 references, including 5142 articles through searching the electronic databases until May 2015 and 2920 articles through screening the reference list of included studies. We excluded 2804 duplicates using EndNote reference manager and 5116 ineligible studies through reading titles and abstracts. Accordingly, we retrieved 142 references for further assessment. We excluded 79 references because they did not meet the inclusion criteria of this meta-analysis. Finally, 63 references remained for meta-analysis (Fig 1) including 25 cohort studies, 3 case-control studies, and 35 cross-sectional studies involving 8,063,634 participants. Fifty-eight studies published in English, two in Spanish [24–26], and three in Korean [27–29] (Table 1).
Thirty-five studies addressed the association between smoking and suicidal ideation [25, 28, 30–62], 8 studies addressed the association between smoking and suicide plan [39, 40, 48, 49, 55, 59–61], 30 studies addressed the association between smoking and suicide attempt [25–27, 29, 30, 32, 34, 37–40, 43, 46–50, 55, 59, 61–71], and 16 studies addressed the association between smoking and suicide death [72–86]. The number of studies presented in the forest plots may be more than the total number of included studies. The reason is that some studies reported the association between smoking and different types of suicidal behaviors simultaneously.
Association between exposure and outcome
The risk of suicidal ideation among current smokers versus nonsmokers is shown in Fig 2. According to this forest plot, there was a significant association between cigarette smoking and suicidal ideation. Current smoking was reliably associated with suicidal ideation. The overall estimate of OR was 2.05 (95% CI: 1.53, 2.58) based on cohort studies and 1.98 (95% CI: 1.72, 2.23) based on case-control/cross-sectional studies. The between-study heterogeneity was high for both groups of studies (P<0.001, I2 = 80.8% and I2 = 81.5%, respectively).
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.
We also assessed the risk of suicidal ideation among former smokers versus nonsmokers (no figure is given). The former smokers were at higher risk for suicidal ideation. The overall estimate of OR was 1.65 (95% CI: 1.09, 2.22; 2 studies; I2 = 0.0%; P = 0.875) on the basis of cohort studies and 1.26 (95% CI: 1.06, 1.46; 5 studies; I2 = 69.1%.1%; P = 0.012) according to case-control/cross-sectional studies.
The risk of suicide plan among current smokers versus nonsmokers is given in Fig 3. This figure indicates a significant association between smoking and suicide plan. Based on this forest plot, the overall estimate of OR was 2.36 (95% CI: 1.69, 3.02). The between-study heterogeneity was high (I2 = 85.2%; P<0.001). No study reported the risk of suicide plan among former smokers.
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.
The risk of suicide attempt among current smokers versus nonsmokers is shown in Fig 4. According to this forest plot, compared to nonsmokers, the current smokers were at higher risk of suicide attempt. The overall estimate of OR was 2.84 (95% CI: 1.49, 4.19) based on cohort studies and 2.14 (95% CI: 1.83, 2.45) based on case-control/cross-sectional studies. The between-study heterogeneity was high for both groups of studies (P<0.001, I2 = 89.6%, I2 = 87.2%, and 35.0%, respectively).
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.
We also explored the risk of suicide attempt among former smokers versus nonsmokers (no figure is given). The association was not statistically significant. The overall estimate of OR was 1.40 (95% CI: 0.50, 3.30; 2 studies; I2 = 46.6%; P = 0.171) based on cohort studies and 1.09 (95% CI: 0.75, 1.43; 5 studies; I2 = 54.8%; P = 0.065) based on case-control/cross-sectional studies.
The risk of suicide death among current smokers versus nonsmokers is given in Fig 5. According to this forest plot, the overall estimate of RR was 1.83 (95% CI: 1.64, 2.02). The between-study heterogeneity was moderate (I2 = 49.7%; P = 0.018).
We investigated the risk of suicide death in former smokers versus nonsmokers (no figure is given). The association was not statistically significant (RR = 1.33; 95% CI: 0.89, 1.78; 7 studies; I2 = 77.6%; P<0.001).
Publication bias was assessed using Begg's and Egger's tests. On the basis of these statistical tests, there was no evidence of publication bias among studies addressing the association between smoking and suicidal ideation (P = 0.306 and P = 0.200), suicide plan (P = 0.621 and P = 0.823), suicide attempt (P = 0.205 and P = 0.821), and suicide death (P = 0.322 and P = 0.484), respectively.
We also explored the possibility of publication bias using Trim and Fill method (Fig 6). This statistical method accounts for publication bias in meta-analysis. The method, a rank-based data augmentation technique, formalizes the use of funnel plots, estimates the number and outcomes of missing studies, and corrects the meta-analysis to incorporate the theoretical missing studies . Based on Trim & Fill method, there was evidence of publication bias among the studies addressing the association between suicidal ideation and smoking. On the basis of this method, the uncorrected OR (before adding the possible missing studies) was 2.00; 95% CI: 1.78, 2.22) and the corrected OR (after adding 9 possible missing studies) was 1.68 (95% CI: 1.47, 1.92). Although there was evidence of publication bias, however, its effect was not significant.
The quality of the studies was explored using NOS scale. According to this scale, there were 42 high-quality studies and 21 low-quality ones (Table 1). We performed subgroup analysis based on the quality of studies and compared the results of high-quality studies with low-quality ones (Table 2). There was no significant difference between the two groups.
Based on the sequential algorithm, the number of studies that had to be omitted from the meta-analysis to drop I2 below the intended threshold (50%) was two for cohort studies addressing the association between smoking and suicide ideation (I2 = 10.5%; OR 2.41; 95% CI: 2.02, 2.80) and four for case-control/cross-sectional ones (I2 = 41.9%; OR 1.653; 95% CI: 1.48, 1.83). Two studies were omitted to drop I2 below the intended threshold for case-control/cross-sectional studies addressing the association between smoking and suicide plan (I2 = 22.3%; OR 2.43; 95% CI: 1.99, 2.86). Finally, the number of studies, which were omitted from the meta-analysis to drop I2 below the desired threshold, was one for cohort studies addressing the association between smoking and suicide attempt (I2 = 0.0%; OR 3.22; 95% CI: 2.99, 3.45) and five for case-control/cross-sectional ones (I2 = 38.9%; OR 2.048; 95% CI: 1.80, 2.29).
In this systematic review, we summarized the available evidence from epidemiological studies exploring the association between smoking habits and suicidal behaviors. Our results suggest that both current and former smokers are at higher risk of suicidal ideation, suicide plan, suicide attempt, and suicide death.
Although the results of this meta-analysis confirmed the association between smoking and suicide, it does not mean causation. In other words, suicidal behaviors are more common among current smokers and the prevalence of smoking habits is higher among suicidal individuals. That means smoking is associated with suicide, but it does not necessarily mean smoking causes suicide. It is still unclear whether smoking influences suicidal behaviors through a biological pathway of smoking itself or whether there is collinearity between smoking and other covariates that are associated with suicide such as psychosocial risk factors or high risk behaviors [9, 11]. Previous epidemiological studies indicated that smoking is part of a pattern of problematic behavior that is linked to various psychopathological disturbances. Several studies reported that smoking is generally associated with psychological disorders and high risk behaviors such as substance and alcohol abuse, sexual and physical abuse, which are considered as major causes of suicide [7, 9, 11, 82, 87]. In addition, a meta-analysis which was conducted by Sankaranarayanan et al in 2015 reported that smoking was significantly associated with an increased risk of suicidality among individuals with a severe mental illness. According to this meta-analysis, the OR of suicidality among psychosis estimated to be 2.12 (95% CI 1.67, 2.7). .
Darvishi et al  conducted a meta-analysis in 2015 to estimate the alcohol-related risk of suicide. They assessed 31 epidemiological studies and reported that alcohol use dependence increases the risk of suicidal ideation 1.86 fold (95% CI: 1.38, 2.35), the risk of suicide attempt 3.13 fold (95% CI: 2.45, 3.81); and the risk of suicide death 2.59 fold (95% CI: 1.95, 3.23). Another meta-analysis was conducted by Poorolajal et al  in 2016 to address the association between substance use disorder and suicidal behaviors. They assessed 43 epidemiological studies and concluded that the substance use disorder was significantly associated with an increased risk of suicidal ideation (OR 2.04; 95% CI: 1.59, 2.50); suicide attempt (OR 2.49; 95% CI: 2.00, 2.98) and suicide death (OR 1.49; 95% CI: 0.97, 2.00). It is likely that part of the association between smoking and suicide reported in this meta-analysis may be explained by the confounding effects of these well-known risk factors. However, another part of the association may be the result of the effect of smoking itself that may increase the risk of suicide through a biological pathway. It is suggested that smoking can significantly decrease the activity of the serotonergic system of the human hippocampus and may reduce brain serotonin function which is negatively related to risk of suicide [89, 90]. Furthermore, nicotine is a potent activator of the hypothalamus, pituitary, adrenal (HPA) axis and is able to activate the attenuated responsiveness of the HPA axis to psychological stress. On the other hand, hyperactivity of the HPA axis is supposed to be a risk factor for suicidal behaviors [91, 92].
This systematic review had a few limitations. First, the results of this meta-analysis are based on the data extracted from observational studies which are associated with the inherent biases that cannot be changed. Furthermore, we were unable to confirm the causal effect of smoking on suicide. Despite these limitations, this meta-analysis could efficiently estimate the relationship between smoking habits and suicidal behaviors. We provided a wide search strategy to enhance the sensitivity of the search to encompass as many studies as possible. We considered all types of observational studies irrespective of age, country, race, publication date, and language. We assessed 8060 articles and included 63 studies with 8,063,634 participants. Therefore, the evidence was sufficient to make a reliable conclusion regarding the objective of this review for estimating the association between smoking habits and suicidal behaviors.
We have high confidence based on the results of studies included in this meta-analysis that smoking is significantly associated with suicidal behaviors. Accordingly, further research is very unlikely to have an important impact on our confidence about the association and is unlikely to change the overall effect. However, limited number of studies explored the dose-response relationship between smoking and suicide. Therefore, further evidence is required to assess the association between the number of cigarettes/day and suicide outcomes.
Our results indicated a smoking-suicide connection. Although this association does not imply causation, but smoking may increase the risk of suicide through affecting on the biological pathways that may increase the risk of suicide or through relationship with other high-risk behaviors such as alcohol and drug dependence. Accordingly, our findings suggest that smoking should be considered as a contributing factor for suicide and smoking prevention and cessation should also be the target of suicide prevention programs.
There is sufficient evidence based on the current epidemiological studies that smoking is significantly associated with an increased risk of suicidal behaviors. Therefore, smoking can be considered as a contributing factor for suicide, although this association does not necessarily imply causation.
We would like to thank the Vice-chancellor of Research and Technology, Hamadan University of Medical Sciences, for financial support of this study.
Conceived and designed the experiments: JP ND. Performed the experiments: JP ND. Analyzed the data: JP. Contributed reagents/materials/analysis tools: JP ND. Wrote the paper: JP.
- 1. World Health Organization. Preventing suicide: A global imperative. Geneva: WHO; 2014.
- 2. Värnik P. Suicide in the world. Int J Environ Res Public Health. 2012; 9(3): 760–771. pmid:22690161
- 3. Miller M, Azrael D, Barber C. Suicide mortality in the United States: the importance of attending to method in understanding population-level disparities in the burden of suicide. Annu Rev Public Health. 2012; 33: 393–408. pmid:22224886
- 4. Centers for Disease Control and Prevention. Understanding suicide: fact sheet. 2013; http://www.cdc.gov/violenceprevention/pub/suicide_factsheet.html, 20 August 2013.
- 5. Poorolajal J, Esmailnasab N, Ahmadzadeh J, Azizi Motlagh T. The burden of premature mortality in Hamadan Province in 2006 and 2010 using standard expected years of potential life lost: a population-based study. Epidemiol Health. 2012; 34: e2012005. pmid:22977738
- 6. Amiri B, Pourreza A, Rahimi Foroushani A, Hosseini SM, Poorolajal J. Suicide and associated risk factors in Hamadan province, west of Iran, in 2008 and 2009. J Res Health Sci. 2012; 12(2): 88–92. pmid:23241517
- 7. Hawton K, Heeringen Kv. Suicide. Lancet. 2009; 373: 1372–1381. pmid:19376453
- 8. Poorolajal J, Rostami M, Mahjub H, Esmailnasab N. Completed suicide and associated risk factors: a six-year population based survey. Arch Iran Med. 2015; 18(1): 39–43. pmid:25556385
- 9. Darvishi N, Farhadi M, Haghtalab T, Poorolajal J. Alcohol-related risk of suicidal ideation, suicide attempt, and completed suicide: a meta-analysis. Plos One. 2015; 10(5): e0126870. pmid:25993344
- 10. Hawton K, Saunders KE, O'Connor RC. Self-harm and suicide in adolescents. Lancet. 2012; 379(9834): 2373–2382. pmid:22726518
- 11. Poorolajal J, Haghtalab T, Farhadi M, Darvishi N. Substance use disorder and risk of suicidal ideation, suicide attempt and suicide death: a meta-analysis. J Public Health. 2016: In press.
- 12. Li D, Yang X, Ge Z, et al. Cigarette smoking and risk of completed suicide: a meta-analysis of prospective cohort studies. J Psychiatr Res. 2012; 46(10): 1257–1266. pmid:22889465
- 13. Moher D, Liberati A, Tetzlaff J, Altman DG. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. Int J Surg. 2010; 8(5): 336–341. pmid:20171303
- 14. World Health Organization. Guidelines for controlling and monitoring the tobacco epidemic. Geneva: WHO; 1998.
- 15. Centers for Disease Control and Prevention. Definitions: self-directed Violence. 2014; [updated 31 December 2013; cited 8 September 2014]; http://www.cdc.gov/violenceprevention/suicide/definitions.html.
- 16. Wells GA, Shea B, O'Connell D, Peterson J, Welch V, Losos M, et al. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses Ontario: Ottawa Hospital Research Institute; 2009 [cited 25 March 2014]. Available from: http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp.
- 17. Higgins JPT, Green S. Cochrane handbook for systematic reviews of interventions Version 5.0.0 [updated February 2008]. The Cochrane Collaboration; 2008: www.cochrane-handbook.org.
- 18. Higgins JPT, Thompson SG, Deeks JJ, Altman D. Measuring inconsistency in meta-analyses. BMJ. 2003; 327: 557–560. pmid:12958120
- 19. Egger M, Davey SG, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ. 1997; 315(7109): 629–634. pmid:9310563
- 20. Begg CB, Mazumdar M. Operating characteristics of a rank correlation test for publication bias. Biometrics. 1994; 50: 1088–1101. pmid:7786990
- 21. Duval S, Tweedie R. A nonparametric "trim and fill" method of accounting for publication bias in meta-analysis. JASA. 2000; 95(449): 89–98.
- 22. DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials. 1986;7:177–188. pmid:3802833
- 23. Patsopoulos NA, Evangelou E, Ioannidis JP. Sensitivity of between-study heterogeneity in meta-analysis: proposed metrics and empirical evaluation. International journal of epidemiology. 2008; 37(5): 1148–1157. pmid:18424475
- 24. Castro-Díaz S, Gómez-Restrepo C, Gil F, Uribe Restrepo M, Miranda C, De La Espriella M, et al. Risk factors for suicidal ideation in patients with depressive disorders in colombia. Revista Colombiana de Psiquiatria. 2013; 43(Suppl 1): 27–35. pmid:26574111
- 25. Pérez-Amezcua B, Rivera-Rivera L, Atienzo EE, de Castro F, Leyva-López A, Chávez-Ayala R. Prevalence and factors associated with suicidal behavior among Mexican students. Prevalencia y factores asociados a la ideación e intento suicida en adolescentes de educación media superior de la República mexicana. 2010; 52(4): 324–333.
- 26. Valdivia M, Silva D, Sanhueza F, Cova F, Melipillán R. Suicide attempts among chilean adolescents. Revista Medica de Chile. 2015; 143(3): 320–328. pmid:26005818
- 27. Park E. The influencing factors on suicide attempt among adolescents in South Korea. Taehan Kanho Hakhoe Chi. 2008; 38(3): 465–473. pmid:18604156
- 28. Park HS, Schepp KG, Jang EH, Koo HY. Predictors of suicidal ideation among high school students by gender in South Korea. J Sch Health. 2006; 76(5): 181–188. pmid:16635202
- 29. Yi S, Yi Y, Jung HS. Factors on the suicidal attempt by gender of middle and high school student. J Korean Acad Nurs. 2011; 41(5): 652–662. pmid:22143214
- 30. Afifi TO, Cox BJ, Katz LY. The associations between health risk behaviours and suicidal ideation and attempts in a nationally representative sample of young adolescents. Can J Psychiatry. 2007; 52(10): 666–674. pmid:18020114
- 31. Almeida OP, Draper B, Snowdon J, Lautenschlager NT, Pirkis J, Byrne G, et al. Factors associated with suicidal thoughts in a large community study of older adults. The British journal of psychiatry: the journal of mental science. 2012; 201(6): 466–472.
- 32. Boden JM, Fergusson DM, Horwood LJ. Cigarette smoking and suicidal behaviour: results from a 25-year longitudinal study. Psychol Med. 2008; 38(3): 433–439. pmid:17892622
- 33. Botega NJ, de Azevedo RCS, Mauro MLF, Mitsuushi GN, Fanger PC, Lima DD, et al. Factors associated with suicide ideation among medically and surgically hospitalized patients. General Hospital Psychiatry. Jul-Aug 2010; 32(4): 396–400. pmid:20633743
- 34. Bronisch T, Hofler M, Lieb R. Smoking predicts suicidality: Findings from a prospective community study. Journal of Affective Disorders. May 2008;108(1–2):135–145. pmid:18023879
- 35. Clarke DE, Eaton WW, Petronis KR, Ko JY, Chatterjee A, Anthony JC. Increased risk of suicidal ideation in smokers and former smokers compared to never smokers: evidence from the Baltimore ECA follow-up study. Suicide Life Threat Behav. 2010; 40(4): 307–318. pmid:20822357
- 36. Dervic K, Akkaya-Kalayci T, Kapusta ND, et al. Suicidal ideation among Viennese high school students. Wien Klin Wochenschr. 2007;119 (5–6): 174–180. pmid:17427021
- 37. Deveci A, Taşkin EO, Erbay Dündar P, Demet MM, Kaya E, Ozmen E, et al. The prevalence of suicide ideation and suicide attempts in Manisa City Centre. Turk Psikiyatri Derg. 2005; 16(3): 170–178. pmid:16180150
- 38. Eaton DK, Foti K, Brener ND, Crosby AE, Flores G, Kann L. Associations between risk behaviors and suicidal ideation and suicide attempts: do racial/ethnic variations in associations account for increased risk of suicidal behaviors among Hispanic/Latina 9th- to 12th-grade female students? Arch Suicide Res. 2011; 15(2): 113–126. pmid:21541858
- 39. Epstein JA, Spirito A. Risk factors for suicidality among a nationally representative sample of high school students. Suicide Life Threat Behav. 2009; 39(3): 241–251. pmid:19606917
- 40. Garrison CZ, McKeown RE, Valois RF, Vincent ML. Aggression, substance use, and suicidal behaviors in high school students. Am J Public Health. 1993; 83(2): 179–184. pmid:8427319
- 41. Goodwin RD, Prescott MR, Tamburrino M, Calabrese JR, Liberzon I, Galea S. Cigarette smoking and subsequent risk of suicidal ideation among National Guard Soldiers. J Affect Disord. 2013; 145(1): 111–114. pmid:23141668
- 42. Hallfors DD, Waller MW, Ford CA, Halpern CT, Brodish PH, Iritani B. Adolescent depression and suicide risk—Association with sex and drug behavior. American Journal of Preventive Medicine. 2004; 27(3): 224–231. pmid:15450635
- 43. Han MA, Kim KS, Ryu SY, Kang MG, Park J. Associations between smoking and alcohol drinking and suicidal behavior in Korean adolescents: Korea Youth Behavioral Risk Factor Surveillance, 2006. Prev Med. 2009; 49(2–3): 248–252. pmid:19573551
- 44. Hintikka J, Koivumaa-Honkanen H, Lehto SM, Tolmunen T, Honkalampi K, Haatainen K, et al. Are factors associated with suicidal ideation true risk factors? A 3-year prospective follow-up study in a general population. Soc Psychiatry Psychiatr Epidemiol. 2009; 44(1):29–33. pmid:18600285
- 45. Hockenberry JM, Timmons EJ, Weg MV. Smoking, parent smoking, depressed mood, and suicidal ideation in teens. Nicotine & Tobacco Research. 2010; 12(3): 235–242.
- 46. Husky MM, Guignard R, Beck F, Michel G. Risk behaviors, suicidal ideation and suicide attempts in a nationally representative French sample. J Affect Disord. 2013; 151(3): 1059–1065. pmid:24070905
- 47. Juan W, Xiao-Juan D, Jia-Ji W, Xin-Wang W, Liang X. The associations between health risk behaviors and suicidal ideation and attempts in an urban Chinese sample of adolescents. Journal of Affect Disord. 2010; 126: 180–187.
- 48. Kessler RC, Berglund PA, Borges G, Castilla-Puentes RC, Glantz MD, Jaeger SA, et al. Smoking and suicidal behaviors in the National Comorbidity Survey: Replication. J Nerv Ment Dis. 2007; 195(5): 369–377. pmid:17502801
- 49. Kessler RC, Borges G, Sampson N, Miller M, Nock MK. The association between smoking and subsequent suicide-related outcomes in the National Comorbidity Survey panel sample. Mol Psychiatry. 2009; 14(12): 1132–1142. pmid:18645572
- 50. Kim SE, Shim JH, Noh H, Hwang HS, Park HK. The relationship between smoking status and suicidal behavior in korean adults: The 4th korea national health and nutrition examination survey (2007 2009). Korean J Fam Med. 2013; 34(3): 178–189. pmid:23730485
- 51. Kumar MB, Walls M, Janz T, Hutchinson P, Turner T, Graham C. Suicidal ideation among Métis adult men and women—associated risk and protective factors: findings from a nationally representative survey. Int J Circumpolar Health. 2012; 71: 18829. pmid:22901287
- 52. Jee SH, Kivimaki M, Kang HC, Park IS, Samet JM, Batty GD. Depression and suicide ideas of cancer patients and influencing factors in South Korea. Asian Pac J Cancer Prev. 2014; 15(7): 2945–2950. pmid:24815429
- 53. Legleye S, Beck F, Peretti-Watel P, Chau N, Firdion JM. Suicidal ideation among young French adults: association with occupation, family, sexual activity, personal background and drug use. J Affect Disord. 2010; 123(1–3): 108–115. pmid:19892406
- 54. McGee R, Williams S, Nada-Raja S. Is cigarette smoking associated with suicidal ideation among young people? Am J Psychiatry. 2005; 162(3): 619–620. pmid:15741485
- 55. Miller M, Borges G, Orozco R, Mukamal K, Rimm EB, Benjet C, et al. Exposure to alcohol, drugs and tobacco and the risk of subsequent suicidality: findings from the Mexican Adolescent Mental Health Survey. Drug Alcohol Depend. 2011; 113(2–3): 110–117. pmid:20801585
- 56. Pfaff JJ, Almeida OP. Detecting suicidal ideation in older patients: identifying risk factors within the general practice setting. Br J Gen Pract. 2005; 55(513): 269–273. pmid:15826433
- 57. Rudatsikira E, Muula AS, Siziya S, Twa-Twa J. Suicidal ideation and associated factors among school-going adolescents in rural Uganda. BMC Psychiatry. 2007; 7: 67. pmid:18034906
- 58. Rudatsikira E, Siziya S, Muula AS. Suicidal ideation and associated factors among school-going adolescents in Harare, Zimbabwe. J Psychol Afr. 2007; 17(1–2): 93–98.
- 59. Silva RJDS, Santos FALD, Soares NMM, Pardono E. Suicidal ideation and associated factors among adolescents in Northeastern Brazil. Scientific World Journal. 2014; 2014: 450943. pmid:25506613
- 60. Wilson ML, Dunlavy AC, Viswanathan B, Bovet P. Suicidal expression among school-attending adolescents in a middle-income sub-Saharan country. Int J Environ Res Public Health. 2012; 9(11): 4122–4134. pmid:23202835
- 61. Wong SS, Zhou B, Goebert D, Hishinuma ES. The risk of adolescent suicide across patterns of drug use: a nationally representative study of high school students in the United States from 1999 to 2009. Soc Psychiatry Psychiatr Epidemiol. 2013; 48(10): 1611–1620. pmid:23744443
- 62. Wu P, Hoven CW, Liu X, Cohen P, Fuller CJ, Shaffer D. Substance use, suicidal ideation and attempts in children and adolescents. Suicide Life Threat Behav. 2004; 34(4): 408–420. pmid:15585462
- 63. Beratis S, Lekka NP, Gabriel J. Smoking among suicide attempters. Compr Psychiatry. 1997; 38(2): 74–79. pmid:9056124
- 64. Berlin I, Hakes JK, Hu MC, Covey LS. Tobacco use and suicide attempt: longitudinal analysis with retrospective reports. PLoS One. 2015; 10(4): e0122607. pmid:25849514
- 65. Bolton JM, Robinson J. Population-attributable fractions of Axis i and Axis II mental disorders for suicide attempts: Findings from a representative sample of the adult, noninstitutionalized US population. Am J Public Health. 2010; 100(12): 2473–2480. pmid:21068419
- 66. Donald M, Dower J, Correa-Velez I, Jones M. Risk and protective factors for medically serious suicide attempts: a comparison of hospital-based with population-based samples of young adults. Aust N Z J Psychiatry. 2006; 40(1): 87–96. pmid:16403044
- 67. Kokkevi A, Richardson C, Olszewski D, Matias J, Monshouwer K, Bjarnason T. Multiple substance use and self-reported suicide attempts by adolescents in 16 European countries. Eur Child Adolesc Psychiatry. 2012; 21(8): 443–450. pmid:22535305
- 68. Riala K, Taanila A, Hakko H, Rasanen P. Longitudinal smoking habits as risk factors for early-onset and repetitive suicide attempts: the Northern Finland 1966 Birth Cohort study. Ann Epidemiol. 2009; 19(5): 329–335. pmid:19230708
- 69. Ursoniu S, Putnoky S, Vlaicu B, Vladescu C. Predictors of suicidal behavior in a high school student population: A cross-sectional study. Wiener Klinische Wochenschrift. 2009; 121(17–18): 564–573. pmid:19890746
- 70. Woods ER, Lin YG, Middleman A, Beckford P, Chase L, DuRant RH. The associations of suicide attempts in adolescents. Pediatrics. 1997; 99(6): 791–796. pmid:9164770
- 71. Zhang J, McKeown RE, Hussey JR, Thompson SJ, Woods JR. Gender differences in risk factors for attempted suicide among young adults: findings from the Third National Health and Nutrition Examination Survey. Ann Epidemiol. 2005; 15(2): 167–174. pmid:15652723
- 72. Angsta J, Claytonb PJ. Personality, smoking and suicide: a prospective study. Journal of Affective Disorders. 1998; 51(1): 55–62. pmid:9879803
- 73. Bohnert KM, Ilgen MA, McCarthy JF, Ignacio RV, Blow FC, Katz IR. Tobacco use disorder and the risk of suicide mortality. Addiction. 2014; 109(1): 155–162. pmid:24134689
- 74. Hemenway D, Solnick SJ, Colditz GA. Smoking and suicide among nurses. Am J Public Health. 1993; 83(2): 249–251. pmid:8427332
- 75. Hemmingsson T, Kriebel D. Smoking at age 18–20 and suicide during 26 years of follow-up-how can the association be explained? Int J Epidemiol. 2003; 32(6): 1000–1004. pmid:14681264
- 76. Iwasaki M, Akechi T, Uchitomi Y, Tsugane S. Cigarette smoking and completed suicide among middle-aged men: a population-based cohort study in Japan. Ann Epidemiol. Apr 2005; 15(4): 286–292. pmid:15780776
- 77. Jee SH, Kivimaki M, Kang HC, Park IS, Samet JM, Batty GD. Cardiovascular disease risk factors in relation to suicide mortality in Asia: prospective cohort study of over one million Korean men and women. Eur Heart J. 2011; 32(22): 2773–2780. pmid:21911340
- 78. Leistikow BN, Martin DC, Samuels SJ. Injury death excesses in smokers: a 1990–95 United States national cohort study. Inj Prev. 2000; 6(4): 277–280. pmid:11144627
- 79. Lucas M, O'Reilly EJ, Mirzaei F, Okereke OI, Unger L, Miller M, et al. Cigarette smoking and completed suicide: results from 3 prospective cohorts of American adults. J Affect Disord. 2013; 151(3): 1053–1058. pmid:24055118
- 80. Miller M, Hemenway D, Bell NS, Yore MM, Amoroso PJ. Cigarette smoking and suicide: a prospective study of 300,000 male active-duty Army soldiers. Am J Epidemiol. 2000; 151(11): 1060–1063. pmid:10873129
- 81. Miller M, Hemenway D, Rimm E. Cigarettes and suicide: a prospective study of 50,000 men. Am J Public Health. 2000; 90(5): 768–773. pmid:10800427
- 82. Paffenbarger RS Jr., Lee IM, Leung R. Physical activity and personal characteristics associated with depression and suicide in American college men. Acta Psychiatr Scand Suppl. 1994; 377: 16–22. pmid:8053361
- 83. Schneider B, Schnabel A, Weber B, Frölich L, Maurer K, Wetterling T. Nicotine use in suicides: A case-control study. European Psychiatry. 2005; 20(2): 129–136. pmid:15797697
- 84. Smith GD, Phillips AN, Neaton HD. Smoking as independent risk factor for suicide: illustration of an artifact from observational epidemiology. The Lancet. 1992; 340: 709–712.
- 85. Sonderman JS, Munro HM, Blot WJ, Tarone RE, McLaughlin JK. Suicides, Homicides, Accidents, and Other External Causes of Death among Blacks and Whites in the Southern Community Cohort Study. Plos One. 2014; 8;9(12): e114852. pmid:25486418
- 86. Tanskanen A, Tuomilehto J, Viinamaki H, Vartiainen E, Lehtonen J, Puska P. Smoking and the risk of suicide. Acta Psychiatr Scand Suppl. 2000; 101: 243–245.
- 87. Tomori M, Zalar B, Plesnicar BK, Ziherl S, Stergar E. Smoking in relation to psychosocial risk factors in adolescents. European Child & Adolescent Psychiatry. 2001; 10(2): 143–150.
- 88. Sankaranarayanan A, Mancuso S, Wilding H, Ghuloum s, Castle D, Smoking, Suicidality and Psychosis: A Systematic Meta-Analysis. PLoS One, 2015;10(9):e0138147.
- 89. Benwell ME, Balfour DJ, Anderson JM. Smoking-associated changes in the serotonergic systems of discrete regions of human brain. Psychopharmacology (Berl). 1990; 102(1): 68–72.
- 90. Malone KM, Waternaux C, Haas GL, Cooper TB, Li S, Mann JJ. Cigarette smoking, suicidal behavior, and serotonin function in major psychiatric disorders. Am J Psychiatry. 2003; 160(4): 773–779. pmid:12668368
- 91. Jokinen J, Carlborg A, Martensson B, Forslund K, Nordstrom AL, Nordstrom P. DST non-suppression predicts suicide after attempted suicide. Psychiatry Res. 2007; 150(3): 297–303. pmid:17316825
- 92. Mann JJ, Currier D, Stanley B, Oquendo MA, Amsel LV, Ellis SP. Can biological tests assist prediction of suicide in mood disorders? Int J Neuropsychopharmacol. 2006; 9(4): 465–474. pmid:15967058