Understanding and transcending “p” requires a functional model of psychopathology: Commentary on Caspi et al. (2026).

Caspi et al. (see record 2026-80066-001) masterfully document the extensive overlap between mental disorders, summarized at the broadest level by the general construct of "p." This overlap seems to leave little room for specificity; moreover, mainstream bottom-up approaches are ill-equipped to address the dual challenge of heterogeneity within diagnostic categories coupled with similarity across the same categories. Here I argue that we can make progress by taking an explicitly functional perspective, and remapping psychopathology onto broad, evolutionarily relevant dimensions of individual variation. I briefly present the fast-slow-defense (FSD) model, a taxonomy of psychopathology based on the evolutionary concept of life history strategies. The FSD model identifies meaningful subtypes within diagnostic categories and reassembles them into broad, functionally distinct spectra with different risk factors and developmental patterns ("lumping via splitting"). In doing so, it simultaneously explains, deconstructs, and goes beyond the descriptive notion of "p," to provide an explanatory framework rooted in biological function. (PsycInfo Database Record (c) 2026 APA, all rights reserved).