White matter alterations in individuals experiencing attenuated positive psychotic symptoms

Diffusion tensor imaging (DTI) studies suggest that reduced fractional anisotropy (FA) in the inferior longitudinal fasciculus (ILF) and superior longitudinal fasciculus (SLF) occurs among schizophrenia patients and those at risk for psychosis. Nevertheless, there is a dearth of knowledge investigating white matter fibre pathways in non-help-seeking individuals who endorse attenuated positive psychotic symptoms (APPS) across a range of mental disorders. The aim of the current study was to determine if alterations in ILF and SLF microstructures were specific to distressing APPS related to risk for psychosis or to APPS symptoms occurring in multiple mental disorders, which would suggest a shared phenotype among disorders.

Twenty-six non-help-seeking young adults were administered the Prodromal Questionnaire. DTI was conducted on participants (n = 13) who endorsed eight or more distressing APPS (D-APPS, a potentially clinically relevant group) and those who endorsed three or fewer distressing APPS (low-APPS; n = 13). Semistructured interviews were administered to determine diagnoses, as well as clinical risk for psychosis status.

Results indicated that the D-APPS group exhibited decreased FA in the left ILF compared with the low-APPS group, even after removing four D-APPS participants who were considered at risk for psychosis.

Findings suggest that white matter microstructure is altered in individuals experiencing APPS across a range of disorders, independent of clinical high risk for psychosis status. Reduced FA in the left ILF may not be specific to psychosis risk, but rather for APPS that occur in a number of mental disorders.