Serum ferritin levels in non-anemic children and adolescents with attention-deficit/hyperactivity disorder: associations with clinical presentations and symptom severity.

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in childhood and adolescence. Iron is involved in dopamine synthesis, myelination, and brain energy metabolism; therefore, reduced iron stores may be relevant to ADHD, although serum ferritin findings remain inconsistent. OBJECTIVE: This study aimed to compare serum ferritin levels between non-anemic children and adolescents with ADHD and controls, and to evaluate their association with ADHD clinical presentations and symptom severity. METHODS: This retrospective cross-sectional analytical study included 105 children and adolescents with DSM-5-TR ADHD and 102 age-comparable controls without known psychiatric or chronic systemic disease, recruited from pediatric outpatient clinics during the same period. Participants with anemia, active systemic disease, intellectual disability, or laboratory evidence of acute inflammation were excluded. Hemoglobin, ferritin, and C-reactive protein (CRP) levels were compared between groups. Same-day ferritin/CRP values from the same institutional laboratory were used. Serum iron samples were obtained in the morning after fasting. Within the ADHD group, iron-related parameters, ADHD presentation, pharmacotherapy/supplementation status, and parent- and teacher-rated Conners scores were evaluated. Non-parametric tests, Spearman correlation analysis, and multivariable logistic regression were performed. RESULTS: The groups were comparable in age, hemoglobin, and CRP. Male sex was more frequent in the ADHD group [77/105 (73.3%) vs. 49/102 (48.0%); p<0.001]. Serum ferritin levels were lower in the ADHD group [15.10 ng/mL, interquartile range (IQR): 11.10-20.60 vs. 20.10 ng/mL, IQR: 15.03-28.33; p<0.001]. After adjustment for age, sex, hemoglobin, and CRP, higher ferritin levels were associated with lower odds of ADHD (OR = 0.927, 95% CI: 0.895-0.961; p<0.001). Ferritin levels differed across ADHD presentations and showed weak negative correlations with parent- and teacher-rated hyperactivity scores. CONCLUSION: Non-anemic children and adolescents with ADHD had lower serum ferritin levels than controls. Ferritin may be a supportive biological parameter in selected ADHD subgroups, but not a diagnostic or severity biomarker.