Level of selected exponents of the kynurenine pathway in patients diagnosed with depression and selected cancers

Altered immune system activity is one of the common pathomechanisms of depressive disorders and cancer. The aim of this study is to evaluate level of selected elements of the kynurenine pathway in groups of depressed and oncological patients. The study included 156 individuals, aged 19–65 years (M = 43.46, SD = 13.99), divided into three groups, namely depressive disorders (DD), oncology patients (OG), and a comparison group of healthy subjects (CG). A sociodemographic questionnaire and the Hamilton Depression Rating Scale (HDRS) were used in the study to assess the intensity of depressive symptoms. Level of TDO2, L-KYN, HK, AA and QA was significantly higher in patients from OG and DD groups than in the comparison group. TDO2 level in the OG group was positively correlated with the severity of depressive symptoms. When the OG and DD groups were analyzed together, level of TDO2, 3-HKYN, AA, QA correlated positively with the severity of depressive symptoms. Thus, kynurenine pathway might play an integral role in the pathogenesis of depression.