Evidence for an Immune Role on Cognition in Schizophrenia: A Systematic Review

Objective: Recent evidence has associated immune and inflammatory changes to cognitive performance in many diseases, including schizophrenia. Since this is a new research field where concepts are not yet solid and new questions and hypothesis are still arising, the present study aimed at summarizing the available clinical data associating schizophrenia, cognition and inflammation/immune function. Methods: A systematic review of the literature was made by searching the following terms in Medline: schizophrenia or psychosis or psychotic AND inflamm* or immun* or cytokine or IL-* or TNF-* or kynureni* or KYNA, AND cognit* or attention or memory or executive function. Results: Seventy five papers were identified using the selected terms, and seven papers were included in the review. Papers excluded focused mainly on basic research or other neuropsychiatric disorders. Conclusions: Recent findings link inflammatory markers to cognition in schizophrenia, suggesting that inflammation is associated with worst cognitive performance. Microglial activation, monoaminergic imbalance, brain abnormalities and the kynurenine pathway are possible mechanisms underlying cognitive impairment in schizophrenia. Clinical trials with addition of immunomodulatory drugs have shown promising results, opening new windows to tackle cognition in schizophrenia.