Circularity, psychiatry & biomarkers: The operationalisation of Alzheimer's & stress in research.

This paper analyses the use of biomarkers in contemporary psychiatric research, arguing that this research has problems of circularity. Focusing on the specific cases of Alzheimer's disease and stress research, we show how these fields have a circular usage of two biomarkers - amyloid-beta and cortisol respectively. We argue that the resulting circularity can be understood as a case of ontological gestalt switching, wherein one object (e.g. Alzheimer's disease) is switched with an object that differs in some way (e.g. protein aggregation). Such circularity can impede research because it entails stripping away important specificities, whereby characteristics that are not directly shared between two switched objects are inevitably forfeited. The losing of specificities can exacerbate discrepancies between illness and disease and lead to the homogenisation of diverse populations and disease subtypes, as has been shown to hamper Alzheimer's research. In response, we suggest that the use of biomarkers in psychiatric research should be subject to guidelines, under which such practices must be articulated in a simplified vocabulary that encourages reflexivity regarding potential instances of circularity.