"Formal thought disorder" in homeless young adults with elevated schizotypal traits: dimensional structure and cognitive correlates

The primary aims were to investigate the dimensional structure and cognitive underpinnings of formal thought disorder (FTD) using the continuum approach. Positive and negative FTD dimensions (PFTD and NFTD) have been distinguished by different cognitive relationships in patients with schizophrenia, but inconsistency in findings may relate to patient-related confounds. The continuum approach of investigating schizophrenia symptoms is free of patient-related confounds, but its suitability to FTD research is uncertain. We performed principal components analysis (PCA) of FTD ratings using the Scale for the Assessment of Thought, Language and Communication (TLC) and the Thought and Language Index (TLI) in a sample (N = 92 and 89, respectively) of homeless young adults with elevated schizotypal traits. Cognitive correlates of the PCA-derived TLC/TLI components were investigated using a comprehensive neuropsychological battery; and we examined whether TLC/TLI components were differentiated by their cognitive relationships. The TLC and TLI showed “clinically-elevated” communicative disturbances. PCA described a three-component TLC solution (“Disorganisation”, “Verbosity”, “Emptiness”) and two-component TLI solution (“Negative”, “Idiosyncratic”), generally consistent with schizophrenia research. TLC “Disorganization” and “Emptiness” ratings, but not TLI ratings, correlated with psychosis-like experiences. Language/semantic and higher-order reasoning dysfunction appeared to drive TLC Disorganisation; while higher-order reasoning and executive dysfunction were the strongest determinants of TLI Negative. Contributions of cognitive dysfunction to TLI Idiosyncratic and TLC Emptiness were less clear; and these were not substantially differentiated from TLC Disorganisation or TLI Negative by their cognitive relationships. Stronger cognitive functioning within this sample, predicted TLC Verbosity, related principally to executive and language/semantic functioning. FTD is associated with schizotypal traits in the general population; FTD is multidimensional in persons with elevated schizotypal traits; language/semantic and higher-order reasoning dysfunction appear to drive PFTD; NFTD primarily relates to higher-order reasoning/executive dysfunction; and the continuum approach to FTD research is supported.