Abstract
There is growing recognition that the risk of attention-deficit hyperactivity disorder (ADHD) in children may be influenced by micronutrient deficiencies, including iron. We conducted this meta-analysis to examine the association between ADHD and iron levels/iron deficiency (ID). We searched for the databases of the PubMed, ScienceDirect, Cochrane CENTRAL, and ClinicalTrials.gov up to August 9th, 2017. Primary outcomes were differences in peripheral iron levels in children with ADHD versus healthy controls (HCs) and the severity of ADHD symptoms in children with/without ID (Hedges’ g) and the pooled adjusted odds ratio (OR) of the association between ADHD and ID. Overall, seventeen articles met the inclusion criteria. Peripheral serum ferritin levels were significantly lower in ADHD children (children with ADHD = 1560, HCs = 4691, Hedges’ g = −0.246, p = 0.013), but no significant difference in serum iron or transferrin levels. In addition, the severity of ADHD was significantly higher in the children with ID than those without ID (with ID = 79, without ID = 76, Hedges’ g = 0.888, p = 0.002), and there was a significant association between ADHD and ID (OR = 1.636, p = 0.031). Our results suggest that ADHD is associated with lower serum ferritin levels and ID. Future longitudinal studies are required to confirm these associations and to elucidate potential mechanisms.
Highlights
There is growing recognition that the risk of attention-deficit hyperactivity disorder (ADHD) in children may be influenced by micronutrient deficiencies, including iron
Twenty-nine articles were excluded for various reasons including a lack of controls, non-clinical trials, not comparing iron between ADHD/controls, or review articles
Our findings not confirm the same results in previous reports and added further information upon current scientific knowledge, such as a higher odds of ADHD and higher severity of ADHD symptoms in the patients with iron deficiency (ID) and significantly lower serum iron level in the children with ADHD compared to the controls in specific post-hoc meta-analysis, such as sensitivity testing
Summary
There is growing recognition that the risk of attention-deficit hyperactivity disorder (ADHD) in children may be influenced by micronutrient deficiencies, including iron. In the most recent meta-analysis, Wang et al updated the evidence of the relationship between iron and ADHD, and revealed significantly lower serum ferritin levels in children with ADHD than in controls (standardized mean difference (SMD) = −0.40, 95% CI = −0.66 to −0.14) but not serum iron (SMD = −0.026, 95% CI = −0.29 to 0.24)[16]. Based on this insignificant result of serum iron in ADHD and controls, the relationship between iron and ADHD still remained unclear. Investigating the relationship between a diagnosis of ID and the risk and severity of ADHD may help to identify potential treatments such as iron supplementation
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