Many studies have evaluated possible associations between the SII, NLR, SIRI, AISI, NLPR with depression, but the results remain controversial.

To determine the association between levels of the systemic inflammatory markers and the prevalence of depression.

Databases like Web of Science, PubMed, Cochrane Library, and EMBASE were searched for relevant studies. Differences in SII, NLR, SIRI, AISI, and NLPR levels between depressed patients and controls were assessed using OR, SMD, and 95 % CI. Subgroup and sensitivity analyses explored heterogeneity based on diagnostic criteria, region, study design, gender, and underlying disease. A meta-analysis was also performed to evaluate the diagnostic effectiveness of inflammatory markers for depression.

A total of 41 studies with 205,438 participants were analyzed. Depressed subjects showed significantly higher NLR (SMD = 0.35, 95 % CI [0.17, 0.53], P < 0.001) and SII (OR = 1.38, 95 % CI [1.15, 1.65], P < 0.001) than controls. Subgroup analyses suggested that diagnostic criteria, study design, and country influence the association. Meta-analysis showed that NLR was effective in diagnosing depression (AUC = 0.70, 95 % CI [0.66, 0.74]), whereas SII was less effective (AUC = 0.37, 95 % CI [0.33, 0.41]).

This study supports the hypothesis that inflammation is associated with depression and that NLR and SII can be a potential predictor, but there are fewer studies related to SIRI, AISI, and NLPR, and further research is needed.