Differences in biomarkers between unipolar and bipolar depression: A meta-analysis

This meta-analysis aims to compare peripheral blood biomarkers between patients with unipolar depression (UD) and bipolar depression (BDD).

PubMed, Embase, the Cochrane Library, and Web of Science were thoroughly retrieved until August 2024. Statistical analyses were performed by Stata 15.1. Weighted mean differences (WMDs) and 95 % confidence intervals (CIs) were calculated for identifying the differences in biomarker between UD and BDD.

31 studies involving 24,923 patients were encompassed. In comparison to UD patients, the BDD cohort displayed significantly higher levels of interleukin-6 (IL-6; WMD = 1.00, 95 % CI: 0.15 to 1.84, p = 0.021), white blood cells (WBC; WMD = 0.59, 95 % CI: 0.23 to 0.96, p = 0.001), neutrophil count (NC) (WMD = 0.32, 95 % CI: 0.12 to 0.52, p = 0.002), uric acid (UA; WMD = 42.00, 95 % CI: 22.45 to 61.54, p < 0.001), and albumin (WMD = 0.75, 95 % CI: 0.17 to 1.33, p = 0.011). Conversely, platelet counts (PC) (WMD = -6.46, 95 % CI: -6.52 to -6.40, p < 0.001) and brain-derived neurotrophic factor (BDNF) levels (WMD = -1583.40, 95 % CI: -2079.26 to -1087.53, p < 0.001) were significantly lower in patients with BDD than in those with UD.

BDD patients exhibited significantly elevated levels of IL-6, WBC, NC, UA, and albumin, and significantly decreased PC and BDNF compared to UD patients. These biomarkers may hold potential utility for differential diagnosis between UD and BDD.