## Abstract

Marginal structural models were developed to account for a so-called time-dependent confounder and to estimate the presumed effect of 'treatment regime' (treatment over time). We present a set of causal axioms, according to which the problem of time-dependent confounding does not exist, and 'treatment regime' affects nothing. Per our axiomatization, marginal structural models do not introduce a new idea of deconfounding, but simply estimate a weighted average of effects. Whenever a weighted average and the weighting scheme can both be rationalized, the models are acceptable. Whenever a weighted average does not estimate an effect (e.g. important effect modification is ignored), or the weights are senseless - the models should not be fit.

Original language | English (US) |
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Pages (from-to) | 214-222 |

Number of pages | 9 |

Journal | Journal of Evaluation in Clinical Practice |

Volume | 19 |

Issue number | 1 |

DOIs | |

State | Published - Feb 2013 |

Externally published | Yes |

## Keywords

- causal diagrams
- derived variables
- inverse probability of treatment weighting
- marginal structural models
- standardization
- thought bias

## ASJC Scopus subject areas

- Health Policy
- Public Health, Environmental and Occupational Health