Time, space and form: Necessary for causation in health, disease and intervention?

Sir Austin Bradford Hill's 'aspects of causation' represent some of the most influential thoughts on the subject of proximate causation in health and disease. Hill compiled a list of features that, when present and known, indicate an increasing likelihood that exposure to a factor causes-or contributes to the causation of-a disease. The items of Hill's list were not labelled 'criteria', as this would have inferred every item being necessary for causation. Hence, criteria that are necessary for causation in health, disease and intervention processes, whether known, knowable, or not, remain undetermined and deserve exploration. To move beyond this position, this paper aims to explore factors that are necessary in the constitution of causative relationships between health, disease processes, and intervention. To this end, disease is viewed as a causative pathway through the often overlapping stages of aetiology, pathology and patho-physiology. Intervention is viewed as a second, independent causative pathway, capable of causing changes in health for benefit or harm. For the natural course of a disease pathway to change, we argue that intervention must not only occupy the same time and space, but must also share a common form; the point at which the two pathways converge and interact. This improved conceptualisation may be used to facilitate the interpretation of clinical observations and inform future research, particularly enabling predictions of the mechanistic relationship between health, disease and intervention.