As a health psychologist mostly involved in the analysis of data I’m used to thinking about variables and the relationships between them – the model. In fact, it is hard to imagine what else you should be thinking about when designing studies or analysing data.
Diagrams should always be helpful; if you can’t draw your model, it suggests that you don’t really understand the model (or that the model is too complicated to draw, or that you have lost your pencil).
I’m often taken aback when diagrams simply don’t depict the model. Take this, for example, from The psychological and social needs of patients (BMA 2011):
“A model of the main determinants of health (see figure 1 below) highlights some of the key factors determining the health of populations. This model demonstrates that there are layers of influence on health that can be modified to improve health”
This is not a model. It’s barely even a diagram, more a contorted list of some factors affecting health, namely:
The question is: how exactly do all these factors affect health, either directly or indirectly, and where should we intervene, i.e. what is the model?