Cited by 4,618Genetic Associations and EpidemiologyAdvanced Causal Inference TechniquesStatistical Methods in Epidemiology

Mendelian randomization: Using genes as instruments for making causal inferences in epidemiology

Lawlor, Debbie A., Harbord, Roger M., Sterne, Jonathan A. C., Timpson, Nic, Davey Smith, George·2008·Statistics in Medicine

Abstract

Observational epidemiological studies suffer from many potential biases, from confounding and from reverse causation, and this limits their ability to robustly identify causal associations. Several high‐profile situations exist in which randomized controlled trials of precisely the same intervention that has been examined in observational studies have produced markedly different findings. In other observational sciences, the use of instrumental variable (IV) approaches has been one approach to strengthening causal inferences in non‐experimental situations. The use of germline genetic variants that proxy for environmentally modifiable exposures as instruments for these exposures is one form of IV analysis that can be implemented within observational epidemiological studies. The method has been referred to as ‘Mendelian randomization’, and can be considered as analogous to randomized controlled trials. This paper outlines Mendelian randomization, draws parallels with IV methods, provides examples of implementation of the approach and discusses limitations of the approach and some methods for dealing with these. Copyright © 2007 John Wiley & Sons, Ltd.

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Crossref · 10.1002/sim.3034

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  • Violation of the exclusion restriction criteria could bias causal estimates in IV analyses when used to test effects of intermediates in RCTs or when used in observational data (including MR).

    “Similarly, violation of the ‘exclusion restriction criteria’33–37 could bias causal estimates in IV analyses when used to test effects of intermediates in RCTs or when used in observational data (including MR)”

    From Triangulation in aetiological epidemiology (2017) · cites this paper as [33]

  • MR studies may be confounded by population stratification.

    “but may be confounded by population stratification.33,34”

    From Triangulation in aetiological epidemiology (2017) · cites this paper as [33]

  • Vertical pleiotropy can shed light on differences in treatments (e.g. PCSK9 and HMGCR) on intermediaries (e.g. blood metabolic markers), which can then be used to explore whether such differences are clinically relevant.

    “Can shed light on differences in treatments (e.g. PCSK9 and HMGCR) on intermediaries (e.g. blood metabolic markers 106 ), which can then be used to explore whether such differences are clinically”
  • Mendelian randomization generally assesses cumulative effects of a risk factor over a long period of the life course without requiring repeat risk factor assessment and with little chance of regression dilution bias or reverse causation.

    “Whereas one of the noted advantages of MR is that it generally assesses the cumulative effects of a risk factor over a long period of the life course (potentially from conception) without requiring repeat risk factor assessment and with little chance of regression dilution bias or reverse causation (confounding by prevalent disease), 7”
  • Concerns about independence of genetic variants from confounders are greater for traits that are more socially-patterned, as this increases susceptibility to associations arising from population structure, assortative mating, and dynastic effects.

    “Concerns about independence are greater for traits that are more socially-patterned, as this increases susceptibility to associations arising from population structure, assortative mating, and dynastic effects 48 .”

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Authors
Lawlor, D. A., Harbord, R. M., Sterne, J. A. C., Timpson, N., & Davey Smith, G.
Affiliations
University of Bristol (GB)
Corresponding author
Lawlor, Debbie A.
Venue
Statistics in Medicine
Publisher
Wiley
Published
2008-02-26
Volume
27
Issue
8
Pages
1133-1163
ISSN
  • 0277-6715 (ISSN-L)
  • 1097-0258
OpenAlex
W1972696558
Cited by
4,618
References
138
Citations by year
2026: 301 · 2025: 616 · 2024: 1082 · 2023: 646 · 2022: 394 · 2021: 298 · 2020: 236 · 2019: 170 · 2018: 161 · 2017: 116 · 2016: 128 · 2015: 100 · 2014: 88 · 2013: 73 · 2012: 74
FWCI
17.31
Type
journal article
Language
en
Open access
closed
Locations
  • Statistics in Medicine (publishedVersion)
  • PubMed (publishedVersion)
  • Explore Bristol Research (submittedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic Associations and Epidemiology
  • Physical Sciences › Mathematics › Statistics and Probability › Advanced Causal Inference Techniques
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
Keywords
Mendelian randomization, instrumental variables, causal inference, observational bias, confounding, reverse causality, germline genetic variants, environmental exposure, randomized controlled trials
MeSH terms
Epidemiologic Methods, Genotype, Humans, Genome, Human, Bias, Causality, Randomized Controlled Trials as Topic, Models, Econometric, Molecular Epidemiology, Genetic Diseases, Inborn

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