Abstract
Background
The link between systemic inflammation and depression has been deeply investigated, but relatively few studies explored symptom‐specific associations, mostly focusing on common inflammatory biomarkers like C‐reactive protein (CRP) levels.
Methods
We investigated associations of low‐grade inflammation with depressive symptoms assessed through a reduced version of Patient Health Questionnaire 9 (PHQ‐9) in a large population‐based cohort of adult Italians (N = 13 301). We built logistic regressions between each depressive symptom and composite index of systemic inflammation based on four circulating biomarkers, namely CRP, Plt, WBC, and GLR (INFLA)‐score, a composite blood‐based inflammation index, and with its component biomarkers, namely CRP, platelets count (Plt), white blood cells count (WBC), and granulocyte‐to‐lymphocyte ratio (GLR).
Results
We observed a strong association of the altered appetite/eating symptom with standardized INFLA‐score (OR [95% CI] = 1.19 [1.12‐1.26]; corrected p = 3.0 × 10−7), CRP (1.28 [1.20‐1.36]; p = 1.9 × 10−13), and WBC (1.13 [1.06‐1.20]; p = 2.3 × 10−3), and of tiredness/low energy with GLR (1.11 [1.05‐1.17]; p = 9.4 × 10−3). These associations remained stable within nondepressed participants (PHQ‐9 < 10), and after adjustment for the use of antidepressants, main chronic conditions, and lifestyle factors; while they were notably attenuated within depressed participants (PHQ‐9 ≥ 10) and—for altered appetite only—by adjustment for obesity.
Conclusions
This study provides a robust replication of the association previously reported between CRP and altered appetite in a large US population cohort, and supports a link between systemic inflammation, altered appetite, and tiredness. Moreover, it extends this evidence to inflammatory markers other than CRP and suggests new targets for the treatment of atypical depression.