Evidence for causal effects of lifetime smoking on risk for depression and schizophrenia: a Mendelian randomisation study

AbstractBackgroundSmoking prevalence is higher amongst individuals with schizophrenia and depression compared with the general population. Mendelian randomisation (MR) can examine whether this association is causal using genetic variants identified in genome-wide association studies (GWAS).MethodsWe conducted two-sample MR to explore the bi-directional effects of smoking on schizophrenia and depression. For smoking behaviour, we used (1) smoking initiation GWAS from the GSCAN consortium and (2) we conducted our own GWAS of lifetime smoking behaviour (which captures smoking duration, heaviness and cessation) in a sample of 462690 individuals from the UK Biobank. We validated this instrument using positive control outcomes (e.g. lung cancer). For schizophrenia and depression we used GWAS from the PGC consortium.ResultsThere was strong evidence to suggest smoking is a risk factor for both schizophrenia (odds ratio (OR) 2.27, 95% confidence interval (CI) 1.67–3.08, p < 0.001) and depression (OR 1.99, 95% CI 1.71–2.32, p < 0.001). Results were consistent across both lifetime smoking and smoking initiation. We found some evidence that genetic liability to depression increases smoking (β = 0.091, 95% CI 0.027–0.155, p = 0.005) but evidence was mixed for schizophrenia (β = 0.022, 95% CI 0.005–0.038, p = 0.009) with very weak evidence for an effect on smoking initiation.ConclusionsThese findings suggest that the association between smoking, schizophrenia and depression is due, at least in part, to a causal effect of smoking, providing further evidence for the detrimental consequences of smoking on mental health.

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The effect of smoking on multiple sclerosis: a mendelian randomization study

10.1101/2020.06.24.20138834 ◽

2020 ◽

Author(s):

Ruth E Mitchell ◽

Kirsty Bates ◽

Robyn E Wootton ◽

Adil Harroud ◽

J. Brent Richards ◽

...

Keyword(s):

Multiple Sclerosis ◽

Mendelian Randomization ◽

Causal Effect ◽

Association Studies ◽

Meta Analysis ◽

Smoking Initiation ◽

Smoking Behaviour ◽

Genome Wide Association Studies ◽

Genome Wide ◽

Smoking Duration

AbstractThe causes of multiple sclerosis (MS) remain unknown. Smoking has been associated with MS in observational studies and is often thought of as an environmental risk factor. We used two-sample Mendelian Randomization (MR) to examined whether this association is causal using genetic variants identified in genome-wide association studies (GWAS) as associated with smoking. We assessed both smoking initiation and lifetime smoking behaviour (which captures smoking duration, heaviness and cessation). There was very limited evidence for a meaningful effect of smoking on MS susceptibility was measured using summary statistics from the International Multiple Sclerosis Genetics Consortium (IMSGC) meta-analysis, including 14,802 cases and 26,703 controls. There was no clear evidence for an effect of smoking on the risk of developing MS (smoking initiation: odds ratio [OR] 1.03, 95% confidence interval [CI] 0.92-1.61; lifetime smoking: OR 1.10, 95% CI 0.87-1.40). These findings suggest that smoking does not have a detrimental consequence on MS susceptibility. Further work is needed to determine the causal effect of smoking on MS progression.

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Little evidence for an effect of smoking on multiple sclerosis risk: A Mendelian Randomization study

PLoS Biology ◽

10.1371/journal.pbio.3000973 ◽

2020 ◽

Vol 18 (11) ◽

pp. e3000973

Author(s):

Ruth E. Mitchell ◽

Kirsty Bates ◽

Robyn E. Wootton ◽

Adil Harroud ◽

J. Brent Richards ◽

...

Keyword(s):

Multiple Sclerosis ◽

Mendelian Randomization ◽

Causal Effect ◽

Association Studies ◽

Meta Analysis ◽

Smoking Initiation ◽

Smoking Behaviour ◽

Genome Wide Association Studies ◽

Genome Wide ◽

Smoking Duration

The causes of multiple sclerosis (MS) remain unknown. Smoking has been associated with MS in observational studies and is often thought of as an environmental risk factor. We used two-sample Mendelian randomization (MR) to examine whether this association is causal using genetic variants identified in genome-wide association studies (GWASs) as associated with smoking. We assessed both smoking initiation and lifetime smoking behaviour (which captures smoking duration, heaviness, and cessation). There was very limited evidence for a meaningful effect of smoking on MS susceptibility as measured using summary statistics from the International Multiple Sclerosis Genetics Consortium (IMSGC) meta-analysis, including 14,802 cases and 26,703 controls. There was no clear evidence for an effect of smoking on the risk of developing MS (smoking initiation: odds ratio [OR] 1.03, 95% confidence interval [CI] 0.92–1.61; lifetime smoking: OR 1.10, 95% CI 0.87–1.40). These findings suggest that smoking does not have a detrimental consequence on MS susceptibility. Further work is needed to determine the causal effect of smoking on MS progression.

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Smoking and the risk for bipolar disorder: evidence from a bidirectional Mendelian randomisation study

The British Journal of Psychiatry ◽

10.1192/bjp.2019.202 ◽

2019 ◽

pp. 1-7 ◽

Cited By ~ 14

Author(s):

Jentien M. Vermeulen ◽

Robyn E. Wootton ◽

Jorien L. Treur ◽

Hannah M. Sallis ◽

Hannah J. Jones ◽

...

Keyword(s):

Bipolar Disorder ◽

Risk Factor ◽

Mental Health Problems ◽

Causal Effect ◽

Association Studies ◽

Smoking Initiation ◽

Smoking Prevention ◽

Mendelian Randomisation ◽

Genome Wide Association Studies ◽

The Past

BackgroundThere 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.AimsWe 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.MethodWe 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.ResultsAcross 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).ConclusionsThese 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.Declaration of interestW.v.d.B received fees in the past 3 years from Indivior, C&A Pharma, Opiant and Angelini. G.M.G. is a National Institute for Health Research (NIHR) Emeritus Senior Investigator, holds shares in P1vital and has served as consultant, advisor or CME speaker in the past 3 years for Allergan, Angelini, Compass Pathways, MSD, Lundbeck (/Otsuka and /Takeda), Medscape, Minervra, P1Vital, Pfizer, Sage, Servier, Shire and Sun Pharma.

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Cigarette smoking and personality: interrogating causality using Mendelian randomisation

Psychological Medicine ◽

10.1017/s0033291718003069 ◽

2018 ◽

Vol 49 (13) ◽

pp. 2197-2205 ◽

Cited By ~ 1

Author(s):

Hannah M. Sallis ◽

George Davey Smith ◽

Marcus R. Munafò

Keyword(s):

Personality Traits ◽

Association Studies ◽

Smoking Initiation ◽

Mendelian Randomisation ◽

Genome Wide Association Studies ◽

Individual Level ◽

Causal Pathways ◽

Genome Wide ◽

Level Data ◽

Causal Nature

AbstractBackgroundDespite the well-documented association between smoking and personality traits such as neuroticism and extraversion, little is known about the potential causal nature of these findings. If it were possible to unpick the association between personality and smoking, it may be possible to develop tailored smoking interventions that could lead to both improved uptake and efficacy.MethodsRecent genome-wide association studies (GWAS) have identified variants robustly associated with both smoking phenotypes and personality traits. Here we use publicly available GWAS summary statistics in addition to individual-level data from UK Biobank to investigate the link between smoking and personality. We first estimate genetic overlap between traits using LD score regression and then use bidirectional Mendelian randomisation methods to unpick the nature of this relationship.ResultsWe found clear evidence of a modest genetic correlation between smoking behaviours and both neuroticism and extraversion. We found some evidence that personality traits are causally linked to certain smoking phenotypes: among current smokers each additional neuroticism risk allele was associated with smoking an additional 0.07 cigarettes per day (95% CI 0.02–0.12, p = 0.009), and each additional extraversion effect allele was associated with an elevated odds of smoking initiation (OR 1.015, 95% CI 1.01–1.02, p = 9.6 × 10−7).ConclusionWe found some evidence for specific causal pathways from personality to smoking phenotypes, and weaker evidence of an association from smoking initiation to personality. These findings could be used to inform future smoking interventions or to tailor existing schemes.

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Pulmonary function and risk of Alzheimer dementia: two-sample Mendelian randomization study

10.1101/2020.07.28.20163352 ◽

2020 ◽

Author(s):

Tom C. Russ ◽

Sarah E. Harris ◽

G. David Batty

Keyword(s):

Pulmonary Function ◽

Causal Effect ◽

Association Studies ◽

Forced Expiratory Volume ◽

Health Concern ◽

Mendelian Randomisation ◽

Genome Wide Association Studies ◽

Global Public Health ◽

Alzheimer Dementia ◽

Dementia Risk

ABSTRACTDementia is a major global public health concern and in addition to recognised risk factors there is emerging evidence that poorer pulmonary function is linked with subsequent dementia risk. However, it is unclear if this observed association is causal or whether it might result from confounding. Therefore, we present the first two-sample Mendelian randomisation study of the association between pulmonary function and Alzheimer dementia using the most recent genome-wide association studies to produce instrumental variables for both. We found no evidence of a causal effect of reduced Forced Expiratory Volume in 1 second (FEV1) or Forced Vital Capacity (FVC) on Alzheimer dementia risk (both P>0.35). However, the FEV1/FVC ratio was associated with Alzheimer dementia risk with, in fact, superior function predicting an increased dementia risk (OR 1.12, 95%CI 1.02-1.23; P=0.016) which may result from survivor bias. While we can conclude that there is no causal link between impaired pulmonary function and Alzheimer dementia, our study sheds less light on potential links with other types of dementia.

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Causal effect of atrial fibrillation/flutter on chronic kidney disease: A bidirectional two-sample Mendelian randomization study

PLoS ONE ◽

10.1371/journal.pone.0261020 ◽

2021 ◽

Vol 16 (12) ◽

pp. e0261020

Author(s):

Masahiro Yoshikawa ◽

Kensuke Asaba ◽

Tomohiro Nakayama

Keyword(s):

Atrial Fibrillation ◽

Chronic Kidney Disease ◽

Kidney Disease ◽

Odds Ratio ◽

Mendelian Randomization ◽

Causal Effect ◽

Association Studies ◽

European Population ◽

Genome Wide Association Studies ◽

The Uk

Chronic kidney disease (CKD) and atrial fibrillation are both major burdens on the health care system worldwide. Several observational studies have reported clinical associations between CKD and atrial fibrillation; however, causal relationships between these conditions remain to be elucidated due to possible bias by confounders and reverse causations. Here, we conducted bidirectional two-sample Mendelian randomization analyses using publicly available summary statistics of genome-wide association studies (the CKDGen consortium and the UK Biobank) to investigate causal associations between CKD and atrial fibrillation/flutter in the European population. Our study suggested a causal effect of the risk of atrial fibrillation/flutter on the decrease in serum creatinine-based estimated glomerular filtration rate (eGFR) and revealed a causal effect of the risk of atrial fibrillation/flutter on the risk of CKD (odds ratio, 9.39 per doubling odds ratio of atrial fibrillation/flutter; 95% coefficient interval, 2.39–37.0; P = 0.001), while the causal effect of the decrease in eGFR on the risk of atrial fibrillation/flutter was unlikely. However, careful interpretation and further studies are warranted, as the underlying mechanisms remain unknown. Further, our sample size was relatively small and selection bias was possible.

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Cigarette smoking and schizophrenia: Mendelian randomisation study

The British Journal of Psychiatry ◽

10.1192/bjp.2020.116 ◽

2020 ◽

pp. 1-6

Author(s):

Jianhua Chen ◽

Ruirui Chen ◽

Siying Xiang ◽

Ningning Li ◽

Chengwen Gao ◽

...

Keyword(s):

Cigarette Smoking ◽

Association Studies ◽

Smoking Initiation ◽

Sensitivity Analyses ◽

Mendelian Randomisation ◽

Genome Wide Association Studies ◽

Nucleotide Polymorphisms ◽

Complex Behaviour ◽

Asian Populations ◽

Smoking Behaviours

Background The link between schizophrenia and cigarette smoking has been well established through observational studies. However, the cause–effect relationship remains unclear. Aims We conducted Mendelian randomisation analyses to assess any causal relationship between genetic variants related to four smoking-related traits and the risk of schizophrenia. Method We performed a two-sample Mendelian randomisation using summary statistics from genome-wide association studies (GWAS) of smoking-related traits and schizophrenia (7711 cases, 18 327 controls) in East Asian populations. Single nucleotide polymorphisms (SNPs) correlated with smoking behaviours (smoking initiation, smoking cessation, age at smoking initiation and quantity of smoking) were investigated in relation to schizophrenia using the inverse-variance weighted (IVW) method. Further sensitivity analyses, including Mendelian randomisation-Egger (MR-Egger), weighted median estimates and leave-one-out analysis, were used to test the consistency of the results. Results The associated SNPs for the four smoking behaviours were not significantly associated with schizophrenia status. Pleiotropy did not inappropriately affect the results. Conclusions Cigarette smoking is a complex behaviour in people with schizophrenia. Understanding factors underlying the observed association remains important; however, our findings do not support a causal role of smoking in influencing risk of schizophrenia.

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Body size and composition and site-specific cancers in UK Biobank: a Mendelian randomisation study

10.1101/2020.02.28.970459 ◽

2020 ◽

Cited By ~ 1

Author(s):

Mathew Vithayathil ◽

Paul Carter ◽

Siddhartha Kar ◽

Amy M. Mason ◽

Stephen Burgess ◽

...

Keyword(s):

Instrumental Variables ◽

Association Studies ◽

Genome Wide Association ◽

Mendelian Randomisation ◽

Genome Wide Association Studies ◽

Uk Biobank ◽

Site Specific ◽

Genome Wide ◽

Increased Risk ◽

The Uk

ABSTRACTObjectivesTo investigate the casual role of body mass index, body fat composition and height in cancer.DesignTwo stage mendelian randomisation studySettingPrevious genome wide association studies and the UK BiobankParticipantsGenetic instrumental variables for body mass index (BMI), fat mass index (FMI), fat free mass index (FFMI) and height from previous genome wide association studies and UK Biobank. Cancer outcomes from 367 586 participants of European descent from the UK Biobank.Main outcome measuresOverall cancer risk and 22 site-specific cancers risk for genetic instrumental variables for BMI, FMI, FFMI and height.ResultsGenetically predicted BMI (per 1 kg/m2) was not associated with overall cancer risk (OR 0.99; 95% confidence interval (CI) 0-98-1.00, p=0.105). Elevated BMI was associated with increased risk of stomach cancer (OR 1.15, 95% (CI) 1.05-1.26; p=0.003) and melanoma (OR 0.96, 95% CI 0.92-1.00; p=0.044). For sex-specific cancers, BMI was positively associated with uterine cancer (OR 1.08, 95% CI 1.01-1.14; p=0.015) but inversely associated with breast (OR 0.95, 95% CI 0.92-0.98; p=0.001), prostate (OR 0.95, 95% CI 0.92-0.99; p=0.007) and testicular cancer (OR 0.89, 95% CI 0.81-0.98; p=0.017). Elevated FMI (per 1 kg/m2) was associated with gastrointestinal cancer (stomach cancer OR 4.23, 95% CI 1.18-15.13, p=0.027; colorectal cancer OR 1.94, 95% CI 1.23-3.07; p=0.004). Increased height (per 1 standard deviation, approximately 6.5cm) was associated with increased risk of overall cancer (OR 1.06; 95% 1.04-1.09; p = 2.97×10-8) and most site-specific cancers with the strongest estimates for kidney, non-Hodgkin lymphoma, colorectal, lung, melanoma and breast cancer.ConclusionsThere is little evidence for BMI as a casual risk factor for cancer. BMI may have a causal role for sex-specific cancers, although with inconsistent directions of effect, and FMI for gastrointestinal malignancies. Elevated height is a risk factor for overall cancer and multiple site cancers.

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Personality, lifestyle and job satisfaction: causal association between neuroticism and job satisfaction using Mendelian randomisation in the UK biobank cohort

Translational Psychiatry ◽

10.1038/s41398-020-0691-3 ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Gull Rukh ◽

Junhua Dang ◽

Gaia Olivo ◽

Diana-Maria Ciuculete ◽

Mathias Rask-Andersen ◽

...

Keyword(s):

Physical Activity ◽

Job Satisfaction ◽

Association Studies ◽

Sensitivity Analyses ◽

Mendelian Randomisation ◽

Genome Wide Association Studies ◽

Single Variable ◽

Causal Association ◽

Uk Biobank ◽

The Uk

AbstractJob-related stress has been associated with poor health outcomes but little is known about the causal nature of these findings. We employed Mendelian randomisation (MR) approach to investigate the causal effect of neuroticism, education, and physical activity on job satisfaction. Trait-specific genetic risk score (GRS) based on recent genome wide association studies were used as instrumental variables (IV) using the UK Biobank cohort (N = 315,536). Both single variable and multivariable MR analyses were used to determine the effect of each trait on job satisfaction. We observed a clear evidence of a causal association between neuroticism and job satisfaction. In single variable MR, one standard deviation (1 SD) higher genetically determined neuroticism score (4.07 units) was associated with −0.31 units lower job satisfaction (95% confidence interval (CI): −0.38 to −0.24; P = 9.5 × 10−20). The causal associations remained significant after performing sensitivity analyses by excluding invalid genetic variants from GRSNeuroticism (β(95%CI): −0.28(−0.35 to −0.21); P = 3.4 x 10−15). Education (0.02; −0.08 to 0.12; 0.67) and physical activity (0.08; −0.34 to 0.50; 0.70) did not show any evidence for causal association with job satisfaction. When genetic instruments for neuroticism, education and physical activity were included together, the association of neuroticism score with job satisfaction was reduced by only −0.01 units, suggesting an independent inverse causal association between neuroticism score (P = 2.7 x 10−17) and job satisfaction. Our findings show an independent causal association between neuroticism score and job satisfaction. Physically active lifestyle may help to increase job satisfaction despite presence of high neuroticism scores. Our study highlights the importance of considering the confounding effect of negative personality traits for studies on job satisfaction.

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Investigating the potential effect of antihypertensive medication on psychiatric disorders: a mendelian randomisation study

10.1101/2020.03.19.20039412 ◽

2020 ◽

Author(s):

Solal Chauquet ◽

Michael O’Donovan ◽

James Walters ◽

Naomi Wray ◽

Sonia Shah

Keyword(s):

Psychiatric Disorders ◽

Drug Target ◽

Drug Exposure ◽

Causal Effect ◽

Association Studies ◽

Neuropsychiatric Symptoms ◽

Potential Effect ◽

Mendelian Randomisation ◽

Genome Wide Association Studies ◽

Increased Risk

ABSTRACTBackgroundThere is growing evidence from observational studies that drugs used for the prevention and treatment of CVD may cause, exacerbate, or relieve neuropsychiatric symptoms.AimUse Mendelian randomisation (MR) analysis to investigate the potential effect of different antihypertensive drugs on schizophrenia, bipolar disorder and major depressive disorder.MethodsWe conduct two sample MR using expression quantitative trait loci (eQTLs) for antihypertensive drug target genes as genetic instruments, together with summary data from published genome-wide association studies, to investigate the causal effect of changes in drug target gene expression (as proxies of drug exposure) on psychiatric disorders.ResultsA 1 standard deviation lower expression of the ACE gene in blood was associated with 4.0 mmHg (95% CI = 2.7 – 5.3) lower systolic blood pressure, but increased risk of schizophrenia (OR (95% CI) = 1.75 (1.28 – 2.38)). A concordant direction of effect was observed with ACE expression in brain tissue.ConclusionsFindings suggest an adverse effect of lower ACE expression on schizophrenia risk. This warrants further investigation to determine if lowering ACE activity for treatment of hypertension using ACE inhibitors (particularly centrally-acting drugs) may worsen symptoms in patients with schizophrenia, and whether there is any association between ACE inhibitor use and risk of (mainly late-onset) schizophrenia.

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