Conceptual diagrams, models, and frameworks are often used in public health literature to help illustrate relations between health exposures and outcomes. However, it is not always clear what these conceptual tools are describing, what they mean or how best to use, design or present them. In fact, the gaze of even the most critical reader tends to glaze over when suddenly faced with a conceptual diagram that is barely, if at all introduced, let alone explained in the accompanying text.

The online Oxford English Dictionary defines a diagram as a “set of lines, marks, or tracings which represent symbolically the course or results of any action or process” or a “delineation used to symbolize related abstract propositions or mental processes”. Adapted from what Earp and Ennett¹ call a “conceptual model”, we define a conceptual diagram as a “diagram of proposed relationships among a set of concepts, factors, or variables about a particular hypothesis, question, context, problem or topic”. Conceptual diagrams are used to organise and synthesise knowledge, define concepts, provide explanations for causal and associative linkages, generate hypotheses …