A novel conceptual framework for understanding the mechanism of adherence to long term therapies

Gérard Reach

Department of Endocrinology, Diabetes and Metabolic Diseases, Avicenne Hospital, Assistance Publique-Hôpitaux de Paris, and Laboratory of Pedagogy of Health, EA 3412, University Paris 13, CRNH-Idf, Bobigny, France

Abstract: The World Health Organization claimed recently that improving patient adherence to long term therapies would be more beneficial than any biomedical progress. First, however, we must understand its mechanisms. In this paper I propose a novel approach using concepts elaborated in a field rarely explored in medicine, the philosophy of mind. While conventional psychological models (eg, the Health Belief Model) provide explanations and predictions which have only a statistical value, the philosophical assumption that mental states (eg, beliefs) are causally efficient (mental causation) can provide the basis for a causal theory of health behaviors. This paper shows that non-adherence to long term therapies can be described as the medical expression of a philosophical concept, that is, weakness of will. I use philosophical explanations of this concept to suggest a mechanistic explanation of nonadherence. I propose that it results from the failure of two principles of rationality. First, a principle of continence, described by the philosopher Donald Davidson in his explanation of weakness of will. This principle exhorts us to act after having considered all available arguments and according to which option we consider best. However, patients conforming to this principle of continence should rationally be nonadherent. Indeed, when patients face a choice between adherence and non-adherence, they must decide, in general, between a large, but delayed reward (eg, health) and a small, but immediate reward (eg, smoking a cigarette). According to concepts elaborated by George Ainslie and Jon Elster, the force of our desires is strongly influenced by the proximity of reward. This inter-temporal choice theory on one hand, and the mere principle of continence on the other, should therefore lead to nonadherence. Nevertheless, adherence to long term therapies is possible, as a result of the intervention of an additional principle, the principle of foresight, which tells us to give priority to mental states oriented towards the future.

Keywords: patient adherence, chronic diseases, weakness of will, inter-temporal choice, principle of foresight, causal theory of health behaviors, philosophy of mind