Peripheral cytokine levels across psychiatric disorders: A systematic review and network meta-analysis

Immune dysregulated cytokine production is involved in mental diseases. However, the results are inconsistent and the pattern of cytokine alterations has not been compared across disorders. We performed a network impact analysis of cytokine levels for different psychiatric disorders including schizophrenia, major depressive disorder, bipolar disorder, panic disorder, post-traumatic stress disorder and obsessive compressive disorder to evaluate their clinical impact across conditions. Studies were identified by searching the electronic databases up to 31/ 05/2022. A total of eight cytokines, together with (high-sensitivity) C-reactive proteins (hsCRP/CRP) were included in the network meta-analysis. The levels of proinflammatory cytokines, hsCRP/CRP and interleukin 6 (IL-6) were significantly increased in patients with psychiatric disorders when compared to controls. IL-6 showed no significant difference among comparisons between disorders according to the network meta-analysis. Inter-leukin 10 (IL-10) is significantly increased in patients with bipolar disorder compared to major depressive dis -order. Further, the level of interleukin-1 beta (IL-1 beta) was significantly increased in major depressive disorder as compared to bipolar disorder. The level of interleukin 8 (IL-8) varied among these psychiatric disorders based on the network meta-analysis result. Overall, abnormal cytokine levels were found in psychiatric disorders, and some of the cytokines displayed differential characteristics in these disorders, especially IL-8, pointing to a role as potential biomarkers for general and differential diagnosis.

Automated summary

Immune dysregulated cytokine production plays a crucial role in mental diseases. The pattern of cytokine alterations varies across different psychiatric disorders. A network impact analysis was conducted to evaluate the clinical impact of cytokine levels in schizophrenia, major depressive disorder, bipolar disorder, panic disorder, post-traumatic stress disorder, and obsessive-compulsive disorder. The results showed significantly increased levels of proinflammatory cytokines, hsCRP/CRP, and interleukin 6 (IL-6) in patients with psychiatric disorders compared to controls. IL-6 did not show significant differences between disorders according to the network meta-analysis. Interleukin 10 (IL-10) was significantly increased in patients with bipolar disorder compared to major depressive disorder, and interleukin-1 beta (IL-1 beta) was significantly increased in major depressive disorder compared to bipolar disorder. The levels of interleukin 8 (IL-8) varied among these psychiatric disorders based on the network meta-analysis. Overall, abnormal cytokine levels were found in psychiatric disorders, and some cytokines, especially IL-8, showed differential characteristics, suggesting their potential as biomarkers for general and differential diagnosis.