Abstract
Background: Previous literature has demonstrated a strong association between cigarette smoking, suicidal ideation and suicide attempts. This association has not previously been examined in a causal inference framework and could have important implications for suicide prevention strategies.
Aims: We aimed to examine the evidence for an association between smoking behaviours (initiation, smoking status, heaviness, lifetime smoking) and suicidal thoughts or attempts by triangulating across observational and Mendelian randomisation analyses.
Method: First, in the UK Biobank, we calculated observed associations between smoking behaviours and suicidal thoughts or attempts. Second, we used Mendelian randomisation to explore the relationship between smoking and suicide attempts and ideation, using genetic variants as instruments to reduce bias from residual confounding and reverse causation.
Results: Our observational analysis showed a relationship between smoking behaviour, suicidal ideation and attempts, particularly between smoking initiation and suicide attempts (odds ratio, 2.07; 95% CI 1.91-2.26; P < 0.001). The Mendelian randomisation analysis and single-nucleotide polymorphism analysis, however, did not support this (odds ratio for lifetime smoking on suicidal ideation, 0.050; 95% CI -0.027 to 0.127; odds ratio on suicide attempts, 0.053; 95% CI, -0.003 to 0.110). Despite past literature showing a positive dose-response relationship, our results showed no clear evidence for a causal effect of smoking on suicidal ideation or attempts.
Conclusions: This was the first Mendelian randomisation study to explore the effect of smoking on suicidal ideation and attempts. Our results suggest that, despite observed associations, there is no clear evidence for a causal effect.
| Original language | English |
|---|---|
| Pages (from-to) | 701-707 |
| Number of pages | 7 |
| Journal | British Journal of Psychiatry |
| Volume | 217 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 31 Dec 2020 |
Bibliographical note
The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health and Social Care.Data Availability Statement
For the summary-level Mendelian randomisation, we used publicly available summary statistics. For smoking initiation, we used summary data from the GWAS and Sequencing Consortium of Alcohol and Nicotine use GWAS.Reference Liu, Jiang, Wedow, Li, Brazel and Chen27 For suicide attempts, summary statistics from a GWAS conducted in the UK Biobank were used.Reference Ruderfer, Walsh, Aguirre, Tanigawa, Ribeiro and Franklin28 All other analyses were conducted with data from the UK Biobank. This data is available upon request to approved researchers. The current project was conducted with data from UK Biobank, application number 9142.Acknowledgements
We are grateful to the participants of the UK Biobank and the individuals who contributed to each of the previous GWAS analyses conducted, as well as all the research staff who worked on the data collection. This paper used UK Biobank application number 9142.Funding
R.E.W., G.D.S. and M.R.M. are all members of the MRC Integrative Epidemiology Unit at the University of Bristol, funded by the MRC (http://www.mrc.ac.uk; grants MC_UU_00011/1 and MC_UU_00011/7). This study was supported by the NIHR Biomedical Research Centre at the University Hospitals Bristol NHS Foundation Trust and the University of Bristol.
Keywords
- epidemiology
- Mendelian randomisation
- smoking
- Suicide
- tobacco
ASJC Scopus subject areas
- Psychiatry and Mental health
