Exploratory study of the association between blood immune markers and clinical symptoms in adolescent depression: Stratified by body mass index.
Abstract
Background
Major Depressive Disorder (MDD) and obesity are prevalent and burdensome public health issues linked by a complex, bidirectional association potentially driven by systemic inflammation. Nevertheless, this relationship remains poorly understood in adolescents with MDD.
Methods
We enrolled 339 adolescents with MDD and stratified them by body mass index (BMI) into underweight, normal weight, overweight, and obese groups. Depression and anxiety severity were evaluated using the Hamilton Depression (HAMD) and Hamilton Anxiety (HAMA) Rating Scales. Hematological inflammatory markers, including neutrophils, monocytes, lymphocyte, platelets, white blood cells, high-sensitivity C-Reactive Protein (hs-CRP), derived ratios, and systemic immune-inflammation index (SII), were assessed across groups. Linear regression and mediation analyses evaluated associations among clinical symptoms, BMI, and inflammatory markers.
Results
The association between BMI and depressive symptoms differed significantly by sex. Among females, the abnormal BMI group had significantly higher total HAMD scores than the normal-weight group, with the obese group demonstrating a higher score on the cognitive impairment factor of HAMD. Inflammatory markers increased progressively across ascending BMI categories. BMI and blood inflammatory markers were associated with depression severity in adolescents. Neutrophil count and monocyte-to-lymphocyte ratio (MLR) showed significant positive indirect effects, accounting for part of the association between obesity and depressive symptoms.
Conclusions
High BMI correlates with more severe depressive symptoms and increased inflammatory status in adolescents with MDD, especially among females. Systemic inflammation partially accounts for the association between high BMI and depression, suggesting that interventions targeting immune and metabolic pathways may offer additional therapeutic benefits.