Only one study exclusively investigated CRP as an inflammatory marker and a possible kynurenine pathway deregulation in acutely ill inpatients with major depressive disorder (MDD) (N = 35), bipolar disorder (BD) (N = 53), schizoaffective disorder (SZA) (N = 40), and schizophrenia (n = 21) versus healthy controls (N = 92). This evidence concerns the gene CRP and major depressive disorder.