Beyond diagnostic boundaries: Evaluating neurocognitive and biomarker profiles in the psychosis spectrum based on Schneiderian first-rank symptoms.

BACKGROUND

This study aimed to evaluate the neurobiological overlap and divergence between schizophrenia (SZ) and bipolar disorder (BD) subtypes. Specifically, we investigated neurotrophic factors, inflammatory markers, and cognitive functions by categorizing patients based on a lifetime history of Schneiderian first-rank symptoms (FRS) to examine the impact of the "psychotic spectrum" beyond traditional diagnostic boundaries.

METHODS

The study included 90 clinically remitted patients - 30 with SZ, 30 with BD with psychotic features (P-BD), and 30 with BD without psychotic features (NP-BD) - along with 30 healthy controls (HCs). Bipolar patients were grouped based on the lifetime presence of FRS during mood episodes. A comprehensive neurocognitive battery was administered. Serum levels of neurotrophic factors and inflammatory markers were measured. Intergroup differences were analyzed using multinomial logistic regression and correlation analyses.

RESULTS

Both P-BD and SZ groups demonstrated significantly lower performance in executive functions, processing speed, and verbal memory than NP-BD and HC groups. P-BD patients exhibited the highest brain-derived neurotrophic factor (BDNF) levels. C-reactive protein (CRP) was most markedly increased in the SZ group and positively correlated with duration of untreated psychosis and body mass index. Multinomial logistic regression identified processing speed and verbal memory scores, along with serum BDNF, fibroblast growth factor-2 (FGF-2), and CRP, as key discriminating variables.

CONCLUSIONS

Our findings suggest that psychotic symptom history may have a significant effect on neurocognitive and biological profiles. These findings support a dimensional approach to psychosis that extends beyond traditional diagnostic boundaries.