Elevated interleukin-8 levels in the cerebrospinal fluid of patients with Schizophrenia Spectrum Disorders

Introduction In recent years, immunological mechanisms have increasingly been discussed in the context of mental disorders. Schizophrenia, in particular, has become the focus of attention because of the discovery of autoimmune encephalitis with the presentation of psychotic symptoms. In addition, multiple studies have reported the associations of infections or autoimmune diseases with schizophreniform disorders. To identify potential immunological processes in the central nervous system, the analysis of cerebrospinal fluid (CSF) plays an important role. Therefore, this subproject of a larger study analyzed different cytokines, especially interleukin-8 (IL-8) levels, in the CSF of patients with schizophrenia spectrum disorders.

Methods The authors examined the CSF of 40 patients with schizophrenia spectrum disorders who were compared with a mentally healthy control group of 39 patients with idiopathic intracranial hypertension (IIH). A magnetic bead multiplexing immunoassay was used to retrospectively determine different cytokines in the CSF.

Results Significantly higher IL-8 levels in the CSF of the patient group with schizophrenia spectrum disorders were observed compared to the control group (Mean ± SD: 41.83 ± 17.50 pg/mL versus 21.40 ± 7.96 pg/mL; p < 0.001).

Conclusion The main finding of this study is the presence of significantly higher IL-8 concentrations in the CSF of patients with schizophrenia spectrum disorders compared to the control group. This supports the hypothesis that inflammatory processes may be involved in the pathophysiology of a subgroup of patients with schizophrenia spectrum disorders. The additional measurement of IL-8 might be helpful in a multimodal diagnostic work-up for the detection of secondary schizophrenic psychosis. However, the results of the study are limited by its retrospective design, methodological aspects, and the control group with IIH. Further research in this field is needed.