Multiple disorders across individual development: The role of heterotypic continuity-Commentary on Caspi et al....

The expansive and provocative proclamation of Caspi et al. (see record 2026-80066-001)-that mental disorders should not be examined in isolation-receives massive support from their thorough, population-based examinations of assortative mating, intergenerational transmission, and longitudinal "expansion" of conditions/disorders over time within individuals. In short, because transdiagnostic/cross-domain manifestations of mental disorders are normative, standard single-condition conceptions of psychopathology may well be myopic, limiting examinations of etiology, mechanisms, and intervention strategies. I focus on the third prong of their argument (development of different conditions over time), based on the ongoing Dunedin birth-cohort study, bringing into play the construct of heterotypic continuity. This term signifies that predictability and stability pertain not to surface behaviors/diagnoses but to deeper, transdiagnostic proclivities yielding different "phenotypes" over time-casting doubt over the contention that successive, sequential comorbidities of independent conditions are at play. Still, the nature of such proclivities (particularly underlying reasons for the displayed behaviors) remains elusive; theory must be invoked in arguments for heterotypic continuity. Heritable risk, a myriad of independent and dependent life experiences, their complex transactions, and individuals' interpretations of trauma and protection are relevant to the search for heterotypic continuity. Urgent need exists for multidisciplinary work in clinical science and public health undergirded by advances in multilevel, longitudinal investigations, incorporating theory regarding underlying functions of different behavioral displays across development. (PsycInfo Database Record (c) 2026 APA, all rights reserved).