The relationship between serum Interleukin- 6, Interleukin- 18, Interleukin- 2, Eotaxin-1, Monocyte Chemoattractant Protein 1 levels and cognitive functions in treatment-resistant schizophrenia.

BACKGROUND AND HYPOTHESIS: Recently, the view that treatment-resistant schizophrenia(TRS) and non-treatment-resistant schizophrenia(nTRS) may represent distinct diseases with different neurobiological processes, rather than being a continuum of the same disorder, has gained prominence. This study aims to investigate whether there are differences in cognitive functions and inflammatory markers (Interleukin- 6 (IL-6), IL-18, IL-2,Eotaxin-1 (CC motif chemokine-11 (CCL11) and Monocyte Chemoattractant Protein(MCP-1,CCL2)) among healthy controls, nTRS and TRS patients. Furthermore, it seeks to evaluate the potential significance of these differences in predicting TRS as possible biomarkers.

STUDY DESIGN: A total of 90 participants were included in the study, consisting of 30 TRS patients, 30 nTRS patients, and 30 healthy volunteers. The Positive and Negative Syndrome Scale(PANSS) was administered to the patient groups. All participants underwent the Wisconsin Card Sorting Test(WCST), Rey Auditory Verbal Learning Test(R-AVLT), Stroop Test, and Trail Making Test(TMT). Blood samples were collected simultaneously from patients and the control group between 08:00 and 12:00 on the same day as the cognitive tests and measured using ELISA kits.

STUDY RESULTS: No significant differences were found between TRS and nTRS groups except for the error count in TMT Part B. MCP-1 was found to be higher only in the TRS compared to controls. All evaluated inflammatory factors were found to be higher in TRS compared to nTRS and our results remained consistent in the logistic regression model.

CONCLUSIONS: These findings support the hypothesis that TRS is characterized by more intense inflammation and distinct neurobiological mechanisms compared to nTRS.