In:
The British Journal of Psychiatry, Royal College of Psychiatrists, Vol. 218, No. 2 ( 2021-02), p. 88-94
Abstract:
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 OR IVW = 1.46, 95% CI 1.28–1.66, P = 1.44 × 10 −8 , lifetime smoking OR IVW = 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 beta IVW = 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.
Type of Medium:
Online Resource
ISSN:
0007-1250
,
1472-1465
DOI:
10.1192/bjp.2019.202
Language:
English
Publisher:
Royal College of Psychiatrists
Publication Date:
2021
detail.hit.zdb_id:
2021500-9
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