DAGitty

To the Editor: Causal diagrams, also known as directed acyclic graphs,1,2 provide an entirely graphical, yet mathematically rigorous methodology for minimizing bias in epidemiologic studies.3,4 The analysis of causal diagrams can be cumbersome in practice, and lends itself well to automatization by a computer program. Important first steps in this regard include the development of the DAG program by Knüppel and Stang5 and dagR by Breitling.6 We announce the release of DAGitty, which provides a graphical user interface tailored to draw and analyze causal diagrams. DAGitty overcomes some performance obstacles (pointed out by Breitling6) that affect earlier software when analyzing large diagrams. The performance…