Robyn E Wootton1,2,3, Harriet S R Greenstone4, Abdel Abdellaoui5, Damiaan Denys5, Karin J H Verweij5, Marcus R Munafò1,2,3, Jorien L Treur5. 1. School of Psychological Science, University of Bristol, MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK. 2. National Institute for Health Research Biomedical Research Centre, University Hospitals Bristol NHS Foundation Trust and University of Bristol, Bristol, UK. 3. MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK. 4. Avon and Wiltshire Mental Health Partnership NHS Trust, Bath, UK. 5. Department of Psychiatry, Amsterdam UMC, University of Amsterdam, Amsterdam, the Netherlands.
Abstract
BACKGROUND AND AIMS: Loneliness is associated with cigarette smoking and problematic alcohol use. Observational evidence suggests these associations arise because loneliness increases substance use; however, there is potential for reverse causation (problematic drinking damages social networks, leading to loneliness). With conventional epidemiological methods, controlling for (residual) confounding and reverse causality is difficult. This study applied Mendelian randomization (MR) to assess bidirectional causal effects among loneliness, smoking behaviour and alcohol (mis)use. MR uses genetic variants as instrumental variables to estimate the causal effect of an exposure on an outcome, if the assumptions are satisfied. DESIGN: Our primary method was inverse-variance weighted (IVW) regression and the robustness of these findings was assessed with five different sensitivity methods. SETTING: European ancestry. PARTICIPANTS: Summary-level data were drawn from the largest available independent genome-wide association studies (GWAS) of loneliness (n = 511 280), smoking (initiation (n = 249 171), cigarettes per day (n = 249 171) and cessation (n = 143 852), alcoholic drinks per week (n = 226 223) and alcohol dependence (n = 46 568). MEASUREMENTS: Genetic variants predictive of the exposure variable were selected as instruments from the respective GWAS. FINDINGS: There was weak evidence of increased loneliness leading to higher likelihood of initiating smoking, smoking more cigarettes, and a lower likelihood of quitting smoking. Additionally, there was evidence that initiating smoking increases loneliness [IVW, β = 0.30, 95% confidence interval (CI) = 0.22-0.38, P = 2.8 × 10-13 ]. We found no clear evidence for a causal effect of loneliness on drinks per week (IVW, β = 0.01, 95% CI = -0.11, 0.13, P = 0.865) or alcohol dependence (IVW, β = 0.09, 95% CI = -0.19, 0.36, P = 0.533) nor of alcohol use on loneliness (drinks per week IVW, β = 0.09, 95% CI = -0.02, 0.22, P = 0.076; alcohol dependence IVW, β = 0.06, 95% CI = -0.02, 0.13, P = 0.162). CONCLUSIONS: There appears to be tentative evidence for causal, bidirectional, increasing effects between loneliness and cigarette smoking, especially for smoking initiation increasing loneliness.
BACKGROUND AND AIMS: Loneliness is associated with cigarette smoking and problematic alcohol use. Observational evidence suggests these associations arise because loneliness increases substance use; however, there is potential for reverse causation (problematic drinking damages social networks, leading to loneliness). With conventional epidemiological methods, controlling for (residual) confounding and reverse causality is difficult. This study applied Mendelian randomization (MR) to assess bidirectional causal effects among loneliness, smoking behaviour and alcohol (mis)use. MR uses genetic variants as instrumental variables to estimate the causal effect of an exposure on an outcome, if the assumptions are satisfied. DESIGN: Our primary method was inverse-variance weighted (IVW) regression and the robustness of these findings was assessed with five different sensitivity methods. SETTING: European ancestry. PARTICIPANTS: Summary-level data were drawn from the largest available independent genome-wide association studies (GWAS) of loneliness (n = 511 280), smoking (initiation (n = 249 171), cigarettes per day (n = 249 171) and cessation (n = 143 852), alcoholic drinks per week (n = 226 223) and alcohol dependence (n = 46 568). MEASUREMENTS: Genetic variants predictive of the exposure variable were selected as instruments from the respective GWAS. FINDINGS: There was weak evidence of increased loneliness leading to higher likelihood of initiating smoking, smoking more cigarettes, and a lower likelihood of quitting smoking. Additionally, there was evidence that initiating smoking increases loneliness [IVW, β = 0.30, 95% confidence interval (CI) = 0.22-0.38, P = 2.8 × 10-13 ]. We found no clear evidence for a causal effect of loneliness on drinks per week (IVW, β = 0.01, 95% CI = -0.11, 0.13, P = 0.865) or alcohol dependence (IVW, β = 0.09, 95% CI = -0.19, 0.36, P = 0.533) nor of alcohol use on loneliness (drinks per week IVW, β = 0.09, 95% CI = -0.02, 0.22, P = 0.076; alcohol dependence IVW, β = 0.06, 95% CI = -0.02, 0.13, P = 0.162). CONCLUSIONS: There appears to be tentative evidence for causal, bidirectional, increasing effects between loneliness and cigarette smoking, especially for smoking initiation increasing loneliness.
Authors: Keir Ej Philip; Feifei Bu; Michael I Polkey; Jamie Brown; Andrew Steptoe; Nicholas S Hopkinson; Daisy Fancourt Journal: Lancet Reg Health Eur Date: 2022-01-02
Authors: Alish B Palmos; Vincent Millischer; David K Menon; Timothy R Nicholson; Leonie S Taams; Benedict Michael; Geraint Sunderland; Michael J Griffiths; Christopher Hübel; Gerome Breen Journal: PLoS Genet Date: 2022-03-03 Impact factor: 5.917
Authors: Atiqul Haq Mazumder; Jennifer Barnett; Nina Lindberg; Minna Torniainen-Holm; Markku Lähteenvuo; Kaisla Lahdensuo; Martta Kerkelä; Jarmo Hietala; Erkki Tapio Isometsä; Olli Kampman; Tuula Kieseppä; Tuomas Jukuri; Katja Häkkinen; Erik Cederlöf; Willehard Haaki; Risto Kajanne; Asko Wegelius; Teemu Männynsalo; Jussi Niemi-Pynttäri; Kimmo Suokas; Jouko Lönnqvist; Solja Niemelä; Jari Tiihonen; Tiina Paunio; Aarno Palotie; Jaana Suvisaari; Juha Veijola Journal: Brain Sci Date: 2021-05-23
Authors: Jorien L Treur; Marcus R Munafò; Emma Logtenberg; Reinout W Wiers; Karin J H Verweij Journal: Psychol Med Date: 2021-05-25 Impact factor: 7.723