Related Experiment Video

Updated: Nov 28, 2025

Cigarette Smoke Exposure in Mice using a Whole-Body Inhalation System
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Little evidence for an effect of smoking on multiple sclerosis risk: A Mendelian Randomization study

Ruth E Mitchell1,2, Kirsty Bates2, Robyn E Wootton1,3,4

  • 1Medical Research Council Integrative Epidemiology Unit, University of Bristol, Bristol, United Kingdom.

Plos Biology
|November 30, 2020
PubMed

Insights

This study found no clear evidence that smoking causes multiple sclerosis (MS). Mendelian randomization analysis suggests smoking initiation and lifetime smoking do not increase MS risk.

Area of Science:

  • Neuroimmunology
  • Genetic Epidemiology

Background:

  • The etiology of multiple sclerosis (MS) is complex and not fully understood.
  • Observational studies suggest a link between smoking and increased MS risk, positioning smoking as a potential environmental risk factor.

Purpose of the Study:

  • To investigate the causal relationship between smoking and multiple sclerosis (MS) susceptibility.
  • To differentiate the effects of smoking initiation versus lifetime smoking behavior on MS risk.

Main Methods:

  • Employed two-sample Mendelian randomization (MR) analysis.
  • Utilized genetic variants associated with smoking from genome-wide association studies (GWASs).
  • Analyzed summary statistics from a large International Multiple Sclerosis Genetics Consortium (IMSGC) meta-analysis (14,802 cases, 26,703 controls).

Main Results:

  • Limited evidence for a causal effect of smoking initiation on MS susceptibility (OR 1.03, 95% CI 0.92-1.61).
  • No clear evidence for a causal effect of lifetime smoking behavior on MS susceptibility (OR 1.10, 95% CI 0.87-1.40).

Conclusions:

  • Current evidence does not support a detrimental causal effect of smoking on multiple sclerosis susceptibility.
  • Further research is required to explore the potential causal impact of smoking on MS progression.

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