Using Causal Path Diagrams to Apply Theory to Public Health Law Research

Causal path diagrams—sometimes called “conceptual models”—have become increasingly common in the presentation of theory-driven research schemes across a variety of disciplines. However, there are few clear conventions in current interdisciplinary practice of graphic representation of variables, associations, interactions, and time. Many path diagrams combine elements of process flow charts from the study of systems and organizations; logic models from evaluation science; and formal statistical path analysis as developed originally in genetics and elaborated by empirical sociologists. This presentation will employ interdisciplinary examples of legal interventions to reduce community violence to illustrate and compare variations on types of path diagrams in current use, including respective advantages and pitfalls. A set of simple conventions will be described for using such diagrams as a heuristic tool to visually represent causal models which include key independent and dependent variables, hypothesized mediators, moderators, direct and indirect pathways of effect. The use of these models in public health law research can yield powerful insights into the intended and unintended effects of laws on population health. As conceptual models, causal path diagrams not only map the steps by which law may impact health, but also allow a researcher to more carefully consider the set of measures to be used in developing a scientifically valid study of those important effects. By gaining a greater understanding of the use of conceptual models, particularly in the context of public health law research, researchers can help policymakers to understand the many ways that laws can help to improve health.