# Association of platelet-to-lymphocyte ratio with depression risk: a systematic review and meta-analysis

## TL;DR

This study finds that higher platelet-to-lymphocyte ratio is linked to increased risk of depression, but results should be interpreted carefully due to high variability.

## Contribution

The study provides the first systematic review and meta-analysis on the association between PLR and depression risk.

## Key findings

- Elevated PLR is associated with increased incidence of depressive disorders (OR 1.04).
- PLR levels are significantly higher in depression patients compared to controls (SMD 1.24).
- Stronger associations were found in ischemic stroke and tumor patients, but not in children and adolescents.

## Abstract

The association of platelet-to-lymphocyte ratio (PLR), a simple marker of inflammation, with depressive disorders has aroused widespread attention, which, however, has not been proved by systematic evidence. Therefore, this study intends to systematically assess the association of PLR with the incidence of depressive disorders.

Embase, Cochrane, PubMed, and Web of Science were searched up to April 2025 for studies investigating the association of PLR with the incidence of depressive disorders. The odds ratio (OR) or standardized mean difference (SMD) with 95% confidence interval (CI) was calculated using random-effects models. We assessed the robustness of the results and potential sources of heterogeneity by sensitivity and subgroup analyses, respectively, and evaluated publication bias by funnel plots and Egger’s test. RevMan 5.4 and Stata 18.0 were utilized for analyses.

Twenty-four comparative groups of 25,873 participants were included. PLR as a categorical variable was closely associated with an elevated incidence of depressive disorders (OR 1.04, 95% CI 1.00-1.08, P = 0.04), and PLR as a continuous variable was significantly higher in the depression group than in the control group (SMD 1.24, 95% CI 0.83-1.66, P<0.00001). Subgroup analyses showed a significant association of PLR with the incidence of depressive disorders in ischemic stroke and tumor patients, but this association did not reach statistical significance in children and adolescents.

Elevated PLR is positively associated with the incidence of depressive disorders, suggesting that PLR may serve as a peripheral inflammatory indicator with potential relevance for the early identification and assessment of depressive disorders. This meta-analysis indicates that elevated PLR may be associated with depressive disorders, but substantial heterogeneity (I² = 99%) and potential publication bias warrant cautious interpretation. More large-scale prospective cohort studies across races and regions are required in the future to validate the association between PLR and the incidence of depressive disorders.

https://www.crd.york.ac.uk/prospero/, identifier CRD420251052927.