Cited by 570Advanced Causal Inference TechniquesEvaluation and Performance AssessmentHealth Policy Implementation Science

The DOI matches its Crossref record; 76 of the 76 references it cites were found in a registry or an index; 1 of the 40 sources its claims cite were checked for support.

Natural Experiments: An Overview of Methods, Approaches, and Contributions to Public Health Intervention Research

Open access

Abstract

Population health interventions are essential to reduce health inequalities and tackle other public health priorities, but they are not always amenable to experimental manipulation. Natural experiment (NE) approaches are attracting growing interest as a way of providing evidence in such circumstances. One key challenge in evaluating NEs is selective exposure to the intervention. Studies should be based on a clear theoretical understanding of the processes that determine exposure. Even if the observed effects are large and rapidly follow implementation, confidence in attributing these effects to the intervention can be improved by carefully considering alternative explanations. Causal inference can be strengthened by including additional design features alongside the principal method of effect estimation. NE studies often rely on existing (including routinely collected) data. Investment in such data sources and the infrastructure for linking exposure and outcome data is essential if the potential for such studies to inform decision making is to be realized.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

Natural experiments (NEs) use naturally occurring variation in exposure to evaluate population health interventions that cannot be randomized, but selective exposure is a central threat to causal inference. The paper reviews methods for NE evaluation and argues that inference is strengthened by clear theory, additional design features, and investment in linked routinely collected data.

Key findings

  • NE studies are defined broadly as any event not under researcher control that divides a population into exposed and unexposed groups; because exposure is often selective, studies should model the assignment process and consider alternative explanations even when effects are large and rapid.
  • The paper reviews regression adjustment, propensity score methods, difference-in-differences (DiD), interrupted time series (ITS), synthetic controls, instrumental variables (IVs), and regression discontinuity (RD), noting that combining methods, replication, and falsification tests can strengthen causal inference.
  • Illustrative examples include a 1995 complete pesticide import ban in Sri Lanka associated with a 50% fall in suicide by self-poisoning; Oregon’s 2003 traffic police layoff of more than one-third of the force associated with a 12–14% increase in fatalities; and Scotland’s ban on multipurchase alcohol discounts associated with a 2% decrease in overall sales after adjustment for England and Wales.
  • The paper concludes that continued investment in routinely collected data, population health surveys, and data-linkage infrastructure is essential for NEs to inform policy making.

Methods

  • Design: narrative overview/review of methods, approaches, and contributions of natural experiments to public health intervention research, using the potential outcomes framework to compare RCTs, NEs, and nonexperimental observational studies.
  • Data or sample: no primary study sample; the paper draws on methodological literature and published NE examples, including Sri Lanka’s pesticide ban, Oregon traffic policing, Scotland’s alcohol legislation, California’s tobacco control program, US Head Start, and Mexico’s Oportunidades program.
  • Main analysis: conceptual and methodological synthesis of effect-estimation approaches, their assumptions, strengths, limitations, and strategies for strengthening inference; no new quantitative analysis is reported.

Limitations

  • The paper states that NEs are not the answer to every evaluation question, that it is not always possible to conduct a good NE when an RCT would be impractical, and that method choice is constrained by intervention features, allocation process, comparators, expected impacts, and data availability.
  • The paper states method-specific limitations, including selective exposure, DiD’s common trends assumption, ITS power and autocorrelation concerns, synthetic controls’ lack of conventional statistical inference and donor-pool matching constraints, IVs’ difficulty in finding and justifying valid instruments, and RD’s local effects and bias–precision trade-off.
  • Evident from the text: this is a narrative overview without a described systematic search strategy or formal quality appraisal; the cited examples are illustrative rather than a comprehensive evidence synthesis.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1146/annurev-publhealth-031816-044327

Cites

76 of 76 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Figures

Figure 1 Directed acyclic graphs illustrating the assumptions of instrumental variable (IV) analysis. (a) The variable Z is associated with outcome Y only through its association with exposure X, so it can be considered a valid instrument of X. (b) Z is not a valid instrument owing to a lack of any association with outcome Y. (c) Z is not a valid instrument owing to its association with confounder C. (d) Z is not a valid instrument owing to its direct association with Y.
Figure 1 Directed acyclic graphs illustrating the assumptions of instrumental variable (IV) analysis. (a) The variable Z is associated with outcome Y only through its association with exposure X, so it can be considered a valid instrument of X. (b) Z is not a valid instrument owing to a lack of any association with outcome Y. (c) Z is not a valid instrument owing to its association with confounder C. (d) Z is not a valid instrument owing to its direct association with Y.CC BY-SA · PubMed Central
Figure 2 Probability of receiving treatment in fuzzy and sharp regression discontinuity designs. (a) A fuzzy regression discontinuity: probability of treatment changes gradually at values of the assignment variable close to the cutoff. (b) A sharp regression discontinuity: probability of treatment changes from 0 to 1 at the cutoff. Source: Reproduced from Moscoe (2015) (57) with permission from Elsevier.
Figure 2 Probability of receiving treatment in fuzzy and sharp regression discontinuity designs. (a) A fuzzy regression discontinuity: probability of treatment changes gradually at values of the assignment variable close to the cutoff. (b) A sharp regression discontinuity: probability of treatment changes from 0 to 1 at the cutoff. Source: Reproduced from Moscoe (2015) (57) with permission from Elsevier.CC BY-SA · PubMed Central

Verification

Claims the paper makes

47 Own interpretation · 29 Not checked yet · 1 Supported

Verify all 39 references — free account

Show all 32 claims

  • It may state two separate claims as one. 22
  • Probably not a substantial claim. 26
45 of 45
  • The paper relies on this without support.

    Age, income, and other continuous variables are often used to determine entitlement to social programs such as means-tested welfare benefits.

    “Age, income, and other continuous variables are often used to determine entitlement to social programs, such as means-tested welfare benefits.”
  • The paper relies on this without support.

    Smaller numbers of observations yield less precise estimates.

    “One drawback is that smaller numbers of observations will yield less precise estimates, so the choice involves a trade-off between bias and precision.”
  • The paper relies on this without support.

    Most natural experimental studies are conducted retrospectively, using data collected before the study is planned.

    “Most NE studies are conducted retrospectively, using data collected before the study is planned.”
  • The paper relies on this without support.

    Good-quality natural experimental studies typically use a range of approaches.

    “Good-quality NE studies typically use a range of approaches.”
4 of 4

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Citations

Cites

Show all 76 references

Research works printed but not linked: 4

  1. Acad. Med. Sci., 2007, Identifying the Environmental Causes of Disease: How Should We Decide What to Believe and When to Take Action.
  2. Farr Inst. Health Inf. Res., 2016, Environmental and public health research.
  3. Hernán M, 2017, Causal Inference
  4. House Commons Sci. Technol. Comm, 2016, The Big Data Dilemma. Fourth Report of Session 2015–16.

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Metadata

Authors
Craig, P., Katikireddi, S. V., Leyland, A., & Popham, F.
Affiliations
MRC/CSO Social and Public Health Sciences Unit (GB)
Venue
Annual Review of Public Health
Published
2017-03-20
Volume
38
Issue
1
Pages
39-56
ISSN
  • 0163-7525 (ISSN-L)
  • 1545-2093
OpenAlex
W2516352831
Cited by
570
References
76
Citations by year
2026: 48 · 2025: 53 · 2024: 53 · 2023: 70 · 2022: 67 · 2021: 83 · 2020: 126 · 2019: 31 · 2018: 29 · 2017: 8
FWCI
9.79
Type
journal article
Language
en
Open access
Locations
  • Annual Review of Public Health (publishedVersion, cc-by-sa)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (acceptedVersion, cc-by-sa)
  • PubMed Central (acceptedVersion, cc-by-sa)
  • ENLIGHTEN (Jurnal Bimbingan dan Konseling Islam) (acceptedVersion)
Funders
  • Scottish Government (SPHSU13, SCAF/15/02, SPHSU15)
  • Medical Research Council (MC_UU_12017–13 & MC_UU_12017–15, MC_UU_12017/13, MC_UU_12017/15, MC_UU_12017, SPHSU15, SPHSU13)
Topics
  • Physical Sciences › Mathematics › Statistics and Probability › Advanced Causal Inference Techniques
  • Social Sciences › Public Administration › Evaluation and Performance Assessment
  • Health Sciences › Health Professions › General Health Professions › Health Policy Implementation Science
Keywords
natural experiment, population health interventions, causal inference, administrative data, data linkage, health disparities, public health evidence
MeSH terms
Decision Making, Health Priorities, Humans, Public Health, Research, Socioeconomic Factors, Healthcare Disparities

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