Clinical significance of serum brain-derived neurotrophic factor and serotonin levels in children with tic disorders.

OBJECTIVE

Tic disorders (TD) are diagnosed mainly through clinical observation, and accessible peripheral biomarkers that reflect neurobiological alterations remain limited. Brain-derived neurotrophic factor (BDNF) and serotonin (5-HT) are biologically relevant to synaptic plasticity and neurochemical regulation. This study aimed to investigate serum BDNF and 5-HT levels in children with TD and to explore their associations with disease severity and clinical subtypes.

METHODS

A total of 125 children with TD and 100 age- and sex-matched healthy controls were enrolled. Serum BDNF and 5-HT concentrations were measured using enzyme-linked immunosorbent assay (ELISA). TD patients were further classified into mild and moderate-to-severe groups according to the Yale Global Tic Severity Scale. Biomarker differences across severity strata and TD subtypes were analyzed, and diagnostic performance was assessed using receiver operating characteristic (ROC) curves and logistic regression.

RESULTS

Serum BDNF levels were significantly lower in TD patients than in healthy controls and declined further in moderate-to-severe cases. In contrast, serum 5-HT levels did not differ between mild TD and HC but were significantly reduced in moderate-to-severe TD compared with mild cases. ROC analysis showed that BDNF (AUC 0.705, 95% CI 0.637-0.772) had modest discriminative ability for identifying TD and both BDNF (AUC 0.760, 95% CI 0.678-0.842) and 5-HT (AUC 0.652, 95% CI 0.555-0.749) were useful in distinguishing disease severity. Logistic regression identified sleep disturbances, family history of TD, and decreased BDNF were independently associated with TD.

CONCLUSION

Reduced serum BDNF was associated with disease presence and severity, whereas decreased 5-HT was mainly related to greater symptom severity. Given the modest ROC performance, serum BDNF and 5-HT may provide auxiliary biological information for pediatric tic disorders, but their clinical application requires validation in larger multicenter cohorts.