Neuroinflammatory Biomarkers in Cerebrospinal Fluid From 106 Patients With Recent-Onset Depression Compared With 106 Individually Matched Healthy Control Subjects

Neuroinflammation has been linked to depression; however, neuroinflammatory biomarkers in the cerebrospinal fluid (CSF) have not previously been thoroughly investigated in a large group of patients with recent-onset depression compared with healthy control subjects. We conducted an individually matched case-control study comparing patients with recent-onset depression (ICD-10: F32) to control subjects. Primary outcomes were CSF white cell count (WCC), CSF-to-serum albumin ratio, CSF total protein, and immunoglobulin G (IgG) index. Secondary outcomes were CSF WCC differential count and CSF neutrophil-to-lymphocyte, CSF-to-serum IgG, and CSF-to-plasma glucose ratios. Linear models adjusting for sex and age were applied. We included 106 patients with recent-onset depression (84.0% outpatients) and 106 healthy control subjects. Patients had 18% higher CSF WCC relative to control subjects (relative mean difference [MD]: 1.18; 95% CI: 1.02–1.40; p = .025). CSF WCC differed with depression symptomatology (p = .034), and patients with severe depression (n = 29) had 43% higher CSF WCC relative to control subjects (MD: 1.43; 95% CI: 1.13–1.80, p = .003). Two (1.9%) patients and no controls (0.0%) had CSF WCC above the normal range (>5 × 106/L). No significant differences between groups were observed regarding CSF-to-serum albumin ratio (MD: 1.07; 95% CI: 0.97–1.18; p = .191), CSF total protein (MD: 1.01; 95% CI: 0.94–1.09; p = .775), or IgG index (MD: 1.05; 95% CI: 0.97–1.15; p = .235). Regarding secondary outcomes, the proportion of CSF neutrophils was lower among patients (MD: 0.22; 95% CI: 0.08–0.59; p = .003) relative to control subjects, whereas the remaining outcomes were not significantly different (all p > .06). Patients had higher CSF WCC relative to control subjects, indicating increased neuroimmunologic activation, particularly for severe depression.