Effects of serum hypersensitive C-reactive protein and BMI on cognitive dysfunction in first-episode and drug-naive patients with major depressive disorder

Background Major depressive disorder (MDD) is a mental illness that is highly prevalent worldwide. Besides its core symptoms, the cognitive dysfunction in MDD patients seriously impairs their social functioning and warrants attention. Cognitive dysfunction in MDD may be related to demographic characteristics, serum inflammatory marker levels and Body Mass Index (BMI, calculated as weight divided by height squared, in kg/m²). This study focuses on the cognitive dysfunction and its associated factors in first-episode, drug-naive patients with MDD . Methods The study enrolled overall 116 first-episode, drug-naive patients with MDD and 100 healthy controls (HC) for comparison. Demographic information was obtained from all participants. We used the Chinese version of the MATRICS Consensus Cognitive Battery (MCCB) to assess cognitive function and the 17-item Hamilton Depression Rating Scale (HAMD-17) to evaluate MDD symptoms. Levels of serum inflammatory markers, such as hypersensitive C-reactive protein (hs-CRP), leukocyte (WBC), neutrophil (NEUR), and eosinophil (EO) were measured. Subsequently, multiple linear regression analysis was utilized to determine factors linked to cognitive dysfunction across the five domains with MDD patients. Results In this study, MDD patients exhibited significantly poorer cognitive function across five domains - speed of processing (SOP), attention/vigilance (AV), working memory (WM), verbal learning (VIS), and visual learning (VRB) - compared with HC ( p  < 0.001). Their serum levels of hs-CRP ( p  = 0.022), WBC ( p  = 0.015), and NEUR ( p  < 0.001) were significantly elevated than HC, whereas the level of EO ( p  = 0.031) was significantly lower. The results of Spearman correlation analysis indicated that BMI was connected to cognitive function among MDD patients, specifically in the domains of SOP (r = 0.274, p  = 0.003) and AV (r = 0.189, p  = 0.042). Multiple linear regression analysis indicated that education years and hs-CRP level were significantly influenced by the cognitive function in the VIS domain among patients with MDD. Conclusion Our study shows a potential link between serum hs-CRP levels, BMI and cognitive dysfunction in MDD patients. This indicates that serum hs-CRP could potentially serve as a promising biomarker to forecast cognitive dysfunction in MDD patients, offering significant clinical implications. Additionally, BMI appears to have a certain predictive value regarding cognitive function in patients with MDD.