Causal diagrams for interference

Elizabeth L. Ogburn, Tyler J. VanderWeele

Research output: Contribution to journalArticle

Abstract

The term "interference" has been used to describe any setting in which one subject's exposure may affect another subject's outcome. We use causal diagrams to distinguish among three causal mechanisms that give rise to interference. The first causal mechanism by which interference can operate is a direct causal effect of one individual's treatment on another individual's outcome; we call this direct interference. Interference by contagion is present when one individual's outcome may affect the outcomes of other individuals with whom he comes into contact. Then giving treatment to the first individual could have an indirect effect on others through the treated individual's outcome. The third pathway by which interference may operate is allocational interference. Treatment in this case allocates individuals to groups; through interactions within a group, individuals may affect one another's outcomes in any number of ways. In many settings, more than one type of interference will be present simultaneously. The causal effects of interest differ according to which types of interference are present, as do the conditions under which causal effects are identifiable. Using causal diagrams for interference, we describe these differences, give criteria for the identification of important causal effects, and discuss applications to infectious diseases.

Original languageEnglish (US)
Pages (from-to)559-578
Number of pages20
JournalStatistical Science
Volume29
Issue number4
DOIs
StatePublished - Jan 1 2014

Keywords

  • Causal diagrams
  • Causal inference
  • Contagion
  • DAGs
  • Graphical models
  • Infectiousness
  • Interference
  • Nonparametric identification
  • Social networks
  • Spillover effects

ASJC Scopus subject areas

  • Statistics and Probability
  • Mathematics(all)
  • Statistics, Probability and Uncertainty

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