Vermeulen, Jentien M., Wootton, Robyn E., Treur, Jorien L., Sallis, Hannah M., Jones, Hannah J., Zammit, Stanley ![]() ![]() |
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Abstract
Background There is increasing evidence that smoking is a risk factor for severe mental illness, including bipolar disorder. Conversely, patients with bipolar disorder might smoke more (often) as a result of the psychiatric disorder. Aims We conducted a bidirectional Mendelian randomisation (MR) study to investigate the direction and evidence for a causal nature of the relationship between smoking and bipolar disorder. Method We used publicly available summary statistics from genome-wide association studies on bipolar disorder, smoking initiation, smoking heaviness, smoking cessation and lifetime smoking (i.e. a compound measure of heaviness, duration and cessation). We applied analytical methods with different, orthogonal assumptions to triangulate results, including inverse-variance weighted (IVW), MR-Egger, MR-Egger SIMEX, weighted-median, weighted-mode and Steiger-filtered analyses. Results Across different methods of MR, consistent evidence was found for a positive effect of smoking on the odds of bipolar disorder (smoking initiation ORIVW = 1.46, 95% CI 1.28–1.66, P = 1.44 × 10−8, lifetime smoking ORIVW = 1.72, 95% CI 1.29–2.28, P = 1.8 × 10−4). The MR analyses of the effect of liability to bipolar disorder on smoking provided no clear evidence of a strong causal effect (smoking heaviness betaIVW = 0.028, 95% CI 0.003–0.053, P = 2.9 × 10−2). Conclusions These findings suggest that smoking initiation and lifetime smoking are likely to be a causal risk factor for developing bipolar disorder. We found some evidence that liability to bipolar disorder increased smoking heaviness. Given that smoking is a modifiable risk factor, these findings further support investment into smoking prevention and treatment in order to reduce mental health problems in future generations.
Item Type: | Article |
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Date Type: | Publication |
Status: | Published |
Schools: | Medicine MRC Centre for Neuropsychiatric Genetics and Genomics (CNGG) |
Publisher: | Cambridge University Press (CUP) |
ISSN: | 0007-1250 |
Date of First Compliant Deposit: | 15 October 2019 |
Date of Acceptance: | 14 August 2019 |
Last Modified: | 05 Dec 2024 05:45 |
URI: | https://orca.cardiff.ac.uk/id/eprint/126049 |
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