Inflammatory biomarkers in schizophrenia: Implications for heterogeneity and neurobiology

The longstanding investigation of immune system abnormalities, including inflammation, in schizophrenia has tremendous renewed interest as an area of research. Presently, the field has an unparalleled opportunity to investigate inflammation as a potential biomarker in schizophrenia. In this review, we: 1) summarize evidence for inflammatory biomarkers across the course of illness, 2) discuss relationships between inflammatory markers and psychopathology, cognition, and illness relapse, 3) consider inflammation as a biomarker for metabolic comorbidity, 4) discuss neuroinflammatory imaging biomarkers, 5) consider inflammation as a biomarker of response to treatment in schizophrenia, as well as findings on adjunctive anti-inflammatory treatments in schizophrenia, and 6) review potential mechanisms for the effects of inflammation on the brain, and 7) discuss implications for the future research agenda. Although there is not evidence to support widespread clinical use of inflammation as a biomarker in schizophrenia, future studies in this area show promise towards a greater understanding of the etiopathophysiology of this heterogeneous syndrome, towards new potential diagnostics and therapeutics to reduce risk, alleviate symptoms and improve quality of life in both at-risk and established patient populations.