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 randomisation (MR) to assess bi-directional 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 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 and smoking more cigarettes, and a lower likelihood of quitting smoking. Additionally, there was evidence that initiating smoking increases loneliness (IVW β=0.30 (0.22-0.38), p=2.8x10-13). We found no clear evidence for a causal effect of loneliness on drinks per week (IVW β=0.01 (-0.11, 0.13), p=0.865) or alcohol dependence (IVW β=0.09 (-0.19, 0.36), p=0.533) nor of alcohol use on loneliness (drinks per week IVW β=0.09 (-0.02, 0.22), p=0.076; alcohol dependence IVW β=0.06 (-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.
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 randomisation (MR) to assess bi-directional 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 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 and smoking more cigarettes, and a lower likelihood of quitting smoking. Additionally, there was evidence that initiating smoking increases loneliness (IVW β=0.30 (0.22-0.38), p=2.8x10-13). We found no clear evidence for a causal effect of loneliness on drinks per week (IVW β=0.01 (-0.11, 0.13), p=0.865) or alcohol dependence (IVW β=0.09 (-0.19, 0.36), p=0.533) nor of alcohol use on loneliness (drinks per week IVW β=0.09 (-0.02, 0.22), p=0.076; alcohol dependence IVW β=0.06 (-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.
Original language | English |
---|---|
Number of pages | 7 |
Journal | Addiction |
DOIs | |
Publication status | Published - 29 Jun 2020 |
Research Groups and Themes
- Physical and Mental Health
- Tobacco and Alcohol
Keywords
- alcohol dependence
- alcohol use
- health behaviours
- loneliness
- Mendelian randomization
- smoking behaviour
- social isolation