Dysregulation of kynurenine pathway and potential dynamic changes of kynurenine in schizophrenia: A systematic review and meta-analysis

•Forty-two eligible papers with 4,217 participants were included in the analysis.•Lower TRP levels and higher circulating KYN/TRP ratios existed in subjects with SCZ.•Lower KYN levels were associated with medication-free persons with SCZ.•The KYN levels were higher in subjects with SCZ after antipsychotic treatments when compared with baseline.•The current evidence provides valuable insight of the potential roles of KYN pathway in the pathogenesis of SCZ.