Exploring serum neopterin and zonulin in children with attention-deficit/hyperactivity disorder: A case-control study of gut permeability and immune activation

Abstract

Objective: Emerging evidence suggests gut-brain axis dysregulation and immune activation in ADHD. This study compared serum zonulin (intestinal permeability regulator) and neopterin (cell-mediated immunity marker) between children with ADHD and healthy controls, and explored associations with disease severity. Methods: This case-control study enrolled 42 drug-naïve children with ADHD (combined presentation) and 42 age- and sex-matched healthy controls. Severity was categorised as mild, moderate, or severe using DSM-5-TR criteria. Serum zonulin and neopterin were measured by ELISA. Results: Zonulin was significantly higher in ADHD versus controls (median: 16.30 vs. 12.36 ng/ml; p=0.033). Neopterin showed a non-significant elevation, but both biomarkers demonstrated a strong, statistically significant association with disease severity (p<0.001 for both). A significant positive correlation was observed between zonulin and neopterin (rho=0.941, p<0.001). Exploratory ROC analysis suggested good discriminatory ability for severe ADHD (AUC of neopterin: 0.873; zonulin: 0.847). Logistic regression identified zonulin as independently associated with ADHD case status (OR=1.206, p=0.019). Conclusion: Elevated serum zonulin was independently associated with ADHD. Both biomarkers correlated strongly with symptom severity, and their interrelation suggests a potential link between increased gut permeability and systemic immune activation in more severe forms of ADHD. These molecules are promising exploratory biomarkers for disease staging, warranting further investigation in larger prospective studies.