Why is it hard to assess thought disorder? Clarifying the third domain of psychosis.
Schizophrenia research June 1, 2026 L Palaniyappan, V S Sreeraj, G Venkatasubramanian et al. 5 citations
Formal Thought Disorder (FTD) is strongly linked to poor outcomes and genetic risk in psychosis, yet it remains poorly defined and rarely measured in clinical practice. A systematic review of 50 years of assessment tools (16 rating scales, 32 factor analyses) reveals that research has treated FTD as a natural kind—a latent entity causing observable signs—but empirical evidence contradicts this. Construct definitions are radically heterogeneous, factor structures do not replicate at the item level, and no essential properties are universal. The authors propose measuring FTD as a Constituted Practical Entity: a probabilistic cluster of linguistic-cognitive features whose interaction produces communication failure, with no single feature necessary or sufficient. This framework reconciles FTD's multidimensional nature with measurement and recommends establishing consensus constituents, measuring their interactions, and developing computational tools.