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BackgroundThe pathogenesis of depression remains not fully understood， and previous studies have suggested that the kynurenine pathway （KP） plays an important role in the pathogenesis of major depressive disorder.ObjectiveTo study the difference in serum KP metabolites level between patients with first-episode and recurrent major depressive disorder， and to testify the correlation between KP metabolites level with the severity of depressive symptoms， so as to provide references for the prevention of recurrence.MethodsA total of 136 patients with major depressive disorder who attended the outpatient clinics of the Affiliated Brain Hospital of Guangzhou Medical University from November 2016 to December 2018 and met the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders， fifth edition （DSM-5） diagnostic criteria were included， including 62 patients in the first-episode group and 74 patients in the recurrent group. Meanwhile， 60 healthy subjects were included as control group. All patients were assessed by Hamilton Depression Scale-17 item （HAMD-17）， and serum concentrations of tryptophan （TRP）， kynurenine （KYN） and kynurenic acid （KYNA） were measured by liquid chromatography tandem mass spectrometry （LC-MS/MS）. Then the correlation of HAMD-17 total score and individual item scores with the levels of KP metabolites was tested using partial correlation coefficient.ResultsCompared with the control group， the first-episode group and recurrent group showed a marked decline in TRP concentration （t=-3.044， -4.477， P

Background. The role of childhood maltreatment (CM) is believed to be crucial in the aberrant function of reward circuit in adolescent-onset major depressive disorder (AO-MDD). Nevertheless, the impact of abnormalities in the GP-based reward circuit on the association between CM and the severity of AO-MDD remains largely unknown. Methods. The GP-based resting-state functional connectivity (RSFC) was analyzed in a sample of 75 patients with AO-MDD and 80 healthy controls in order to identify potential abnormalities in the GP-based reward circuit in AO-MDD patients. Furthermore, we investigated the possible associations between aberrant GP-based reward circuit functioning, CM and its subtypes (namely, childhood abuse and childhood neglect), and the severity of AO-MDD. Results. Compared to the healthy control group, patients with AO-MDD demonstrated a reduction in RSFC between the left posterior GP and the right dorsomedial prefrontal cortex (DMPFC). Our moderation analysis revealed that the abnormal RSFC between the posterior GP and DMPFC had a moderating effect on the relationship between CM and the severity of AO-MDD. Furthermore, upon further interaction decomposition, we observed a positive correlation between CM and AO-MDD severity exclusively in patients with AO-MDD who exhibited lower RSFC between the posterior GP and DMPFC. For AO-MDD patients with higher RSFC between posterior GP and DMPFC, the relationship between CM and AO-MDD severity was not discernible. Conclusions. Our findings underscore the crucial role of anomalies in the reward circuit in AO-MDD and furnish novel leads for probing the relationship among CM, malfunctioning of the reward circuit, and AO-MDD. [ABSTRACT FROM AUTHOR]