Abstract
Objective: Attention Deficit Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental disorder in children, characterized by persistent inattention, hyperactivity, and impulsivity. Despite decades of research, its etiology remains incompletely understood. Recent interest has focused on the potential role of vitamin D (Vit D), given its neuroprotective properties and associations with various psychiatric disorders. However, the relationship between Vit D levels and ADHD, especially in children, remains unclear. This study aimed to investigate serum 25-hydroxyvitamin D [25(OH)D] levels in children diagnosed with ADHD compared to age-matched healthy controls.
Methods: This prospective controlled study included 150 children aged 6–18 years: 75 diagnosed with ADHD and 75 healthy controls, all recruited from Istanbul Faculty of Medicine. ADHD diagnoses were confirmed using the KSADS-PL and ADHD Rating Scale-IV. Vit D levels were measured via high-performance liquid chromatography (HPLC) from fasting morning serum samples. Statistical analyses were performed, and a P value of < 0.05 was considered statistically significant.
Results: Baseline sociodemographic variables were similar between groups except for gender distribution, with a higher male proportion in the ADHD group. The mean serum Vit D level was 18.11 ± 5.98 ng/mL in the ADHD group and 18.95 ± 7.27 ng/mL in controls; this difference was not statistically significant (p > 0.05). However, the mean serum Vit D levels in both groups were found to be within the deficient range. Additionally, no significant differences were found among ADHD subtypes (combined, inattentive, hyperactive-impulsive) in terms of mean serum Vit D levels (p>0.05).
Conclusion: This study found no significant difference in mean serum Vit D levels between children with ADHD and healthy controls, nor between ADHD subtypes. These findings suggest that serum Vit D level may not be a distinguishing biomarker for ADHD. However, the presence of Vit D deficiency in both groups suggests that it constitutes a serious public health concern and underscores the need for its inclusion in routine screening programs to mitigate potential adverse outcomes. Further large-scale and longitudinal studies are needed to clarify Vit D’s potential role in ADHD pathophysiology.

Key words: ADHD, Adolescent, Child, Vitamin D