The Association Between Serum Neurofilament Light Chain and Inflammatory Markers in Psychiatric Disorders.

OBJECTIVES: Several studies have found mild elevations of serum neurofilament light chain (sNfL) - a marker of neuroaxonal injury - in various psychiatric disorders (PD) compared to controls. Given the documented role of neuroinflammation in PD, this study investigated the relationship between inflammatory markers and sNfL in a transdiagnostic cohort of PD. METHODS: PD data was obtained from Signature Biobank (BbS) participants aged 40-81 that presented to a psychiatric emergency department with various PDs (n = 291, M = 181, F = 110), and a control group (n = 69, M = 36, F = 33). Serum NfL was measured using SIMOA technology, inflammatory markers interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) were measured using ELISA, and C-reactive protein (CRP) was measured using Atellica CH Wide range method. Linear regression models were used to test associations between sNfL and inflammatory markers while controlling for age, sex, BMI, in addition to identified statistically significant medical/lifestyle covariates of sNfL and the inflammatory markers. RESULTS: In the PD transdiagnostic group, sNfL was positively associated with IL-6 (np2 = .065, p < .001) with a medium effect size and positively associated with TNF-α (np2 = .075, p = .002) with a medium effect size; no associations between CRP and sNfL were detected. At the subgroup levels, the associations remained statistically significant in the mood and psychotic disorders groups, and only for IL-6 in anxiety disorders group. CONCLUSIONS: This study provides evidence of an association between levels of inflammation (IL-6 and TNF-α) and neuroaxonal injury (sNfL) in PD.