The association between serum vitamin D concentration and Attention Deficit/Hyperactivity Disorder: a systematic review and meta-analysis of observational and interventional studies

Abstract Background Attention Deficit/Hyperactivity Disorder (ADHD) is a prevalent psychiatric disorder among children that significantly impacts various aspects of life, including academic performance, peer relationships, and overall daily functioning. Recent research has suggested that vitamin D may play a role in improving ADHD symptoms, although the mechanisms remain unclear. Objectives This systematic review and meta-analysis sought to determine the association between serum vitamin D and ADHD symptoms in children, summarizing evidence from randomized controlled trials (RCTs) and observational studies. Methods This systematic review and meta-analysis followed PRISMA guidelines, evaluating studies published up to 27th April 2025. Eligible studies assessed serum vitamin D levels or supplementation and ADHD symptoms in children aged 6–18 years and in mothers under 40. Meta-analyses were performed to calculate pooled mean differences and odds ratios for ADHD risk associated with vitamin D deficiency. Results A total of 37 studies were included, comprising 30 observational studies and seven RCTs, with a combined sample of 24,336 participants. The pooled mean difference of serum vitamin D concentration between ADHD cases and controls showed a significant difference (–6.55 ng/mL, 95% CI: –8.06, –5.03, p  < 0.001), indicating that children with ADHD had lower vitamin D levels. The overall odds ratio (OR) of ADHD in vitamin D-deficient children from 13 studies was significant (OR 1.97, 95% CI: 1.42, 2.75, p  = 0.009), suggesting an association between vitamin D deficiency and the increased risk of ADHD in children. Vitamin D deficiency and maternal vitamin D deficiency during pregnancy also were significantly associated with ADHD in offspring (OR 1.50, 95% CI: 1.17, 1.91, p  < 0.001). ADHD total scores, inattention scores, and Connor parent questionnaire scores all demonstrated significant improvement with vitamin D supplementation, while hyperactivity scores did not show significant changes. Conclusion This meta-analysis supports an association between low vitamin D levels and increased ADHD risk in children. Supplementation was associated with improvement in some ADHD symptoms, although causal relationships remain unproven; therefore, further high-quality trials are required to establish a clear causal link and optimize vitamin D supplementation strategies for ADHD management.