Is there a natural boundary for formal thought disorder? Evidence from taxometric analysis

AI Summary

Formal thought disorder shows a predominantly dimensional latent structure, present continuously across clinical and healthy populations.
Among healthy individuals, Peculiarities were rare (1.2%), while Loosening occurred in 11.3% and Impoverishment in 8.9%, using conservative thresholds.
Multi-construct co-occurrence exceeded chance but was confined to patients at clinical thresholds, suggesting psychosis risk depends on coalescence of FTD dimensions.

TL;DR (AI Generated)

Clarifying whether FTD is categorical or continuous and its supra-thres hold prevalence in non-clinical populations has direct implications for bears directly on mechanistic studies of FTD, psychosis prediction, and early intervention.

Using complementary taxometric procedures (MAMBAC, MAXEIG, and L-Mode) with simulation of comparison data and multiple thresholding approaches (minimally important change criteria, ROC analysis, intuitive binarization), we evaluated the latent structure of FTD, optimal cutoff points to estimate FTD prevalence, and the frequency of co-occurrence of subconstructs.

Basic summary

Psychol Med. 2026 Oct 26;56:e347. doi: 10.1017/S0033291726106084.

ABSTRACT

BACKGROUND: Formal thought disorder (FTD) has been conceptualized as a categorical syndrome of psychosis, but this remains untested. Clarifying whether FTD is categorical or continuous and its supra-thres hold prevalence in non-clinical populations has direct implications for bears directly on mechanistic studies of FTD, psychosis prediction, and early intervention.

METHODS: In a multi-site cross-sectional study of 520 individuals (352 clinical, 168 non-clinical), we used the Thought and Language Index to assess FTD across three subconstructs: Loosening, Peculiarities, and Impoverishment. Using complementary taxometric procedures (MAMBAC, MAXEIG, and L-Mode) with simulation of comparison data and multiple thresholding approaches (minimally important change criteria, ROC analysis, intuitive binarization), we evaluated the latent structure of FTD, optimal cutoff points to estimate FTD prevalence, and the frequency of co-occurrence of subconstructs.

RESULTS: Taxometric analyses revealed a predominantly dimensional latent structure for FTD across various base rates. Among healthy individuals, Peculiarities were uncommon (1.2%), but 11.3% exhibited Loosening and 8.9% had Impoverishment even with conservative thresholds. Multi-construct co-occurrence exceeded chance across the sample but was restricted to patients at conservative clinical thresholds.

CONCLUSIONS: FTD exists in a continuous dimensional structure extending into healthy populations. Each dimension is measurable in healthy individuals, but multi-dimensional convergence at clinical thresholds (i.e. disorder with functional impairment) appears specific to patients. This suggests that common vulnerability factors increase the likelihood of elevations across multiple but substantially independent dimensions of FTD. As a hypothesis requiring prospective validation, clinical risk of psychosis may depend on the coalescence rather than single-dimensional severity of FTD subconstructs.

PMID:42929241 | DOI:10.1017/S0033291726106084

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