Causal inference and directed acyclic graph: An epidemiological concept much needed for oral submucous fibrosis

Oral submucous fibrosis (OSMF), although already established as an oral potentially malignant disorder (OPMD), still stands over a weak bridge because of its controversial pathogenesis. There has been tremendous work on this disease since 1962, surprisingly, we are unsuccessful in finding the exact causation of OSMF. The potential cause for this is either a lack of systematically performed clinical observational studies or over-interpreted inferences of the presented results. Accordingly, the literature is piled with complex data that is being followed by emerging researchers. Hence, this conceptual paper is presented to focus and explain only the epidemiological concepts of causal inference and the construction of DAGs. These concepts will help to encode our subject matter knowledge and assumptions regarding the causal structure problem, classify the source of systematic bias, identify the potential confounders, potential issues in the study design, and guide the data analysis.