Psychoneural reduction revised: The case of suicidality in bipolar disorder.

This paper uses suicidality in bipolar disorder (BD) to illustrate that multidimensional frameworks account for complex phenomena with cognitive, psychological, socioenvironmental and physiological components better than their reductionist counterparts. We challenge level-based reductionist models that regard a particular dimension as fundamental. To comprehensively understand complex psychiatric phenomena, multidimensional models that acknowledge the heterogeneity of aetiological factors, rather than homogenising them under a single dimension, must be utilised. Multidimensional models allow a better understanding of the individual context under which a psychiatric phenomenon arises, and the interrelationships between its different aetiological dimensions. Suicidality in BD is used as a case study because it particularly highlights the interplay between biological, psychological, sociocultural and experiential factors. The multidimensional nature of suicidality is reflected by the heterogeneous strategies by which it is managed. Although similar to suicidality in other contexts, in BD suicidality has distinctive structural characteristics that emphasise its multidimensionality. Consequently, investigating suicidality in BD yields claims generalisable to suicidality as a whole alongside novel insights on BD-specific features. For instance, suicidality in BD has physiological causal factors, e.g., genetic predisposition and aggravation by symptomatic periods. However, its other features underscore the causal roles of cognitions. In persons with BD, suicidality can persist beyond depression and is sometimes experienced during mania, possibly due to suicidal ideation persisting beyond symptomatic periods. This indicates the need to account for cognitive or psychological causal factors. Models of suicidality in BD typically adopt a non-level-based, non-reductionist approach, reflected in the diverse clinical strategies for managing suicidality in BD.