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Meta-Analysis
. 2017 Jan 3;12(1):e0169145.
doi: 10.1371/journal.pone.0169145. eCollection 2017.

Iron Status in Attention-Deficit/Hyperactivity Disorder: A Systematic Review and Meta-Analysis

Yan Wang  1   2 , Lan Huang  1   2 , Li Zhang  1   2 , Yi Qu  1   2 , Dezhi Mu  1   2   3
Affiliations
Meta-Analysis

Iron Status in Attention-Deficit/Hyperactivity Disorder: A Systematic Review and Meta-Analysis

Yan Wang et al. PLoS One. .

Abstract

Background: Attention-deficit/hyperactivity disorder (ADHD) is one of the most common psychiatric disorders in children. However, the pathogenesis of ADHD remains unclear. Iron, an important trace element, is implicated in brain function and dopaminergic activity. Recent studies have investigated the association between iron deficiency and ADHD, but the results are inconsistent.

Methods: A systemic search of MEDLINE, EMBASE, Web of Science and Cochrane Library databases was supplemented by manual searches of references of key retrieved articles. Study quality was evaluated using the Newcastle-Ottawa Scale. The standardised mean difference (SMD) and 95% confidence intervals (CIs) were calculated using a random-effects model. H2 and I2 were used to evaluate the heterogeneity, and sensitivity, subgroup and meta-regression analyses were conducted to explore the reason of heterogeneity.

Results: The search yielded 11 studies published before July 25, 2016. Of these, 10 studies, comprising 2191 participants and 1196 ADHD cases, reported serum ferritin levels, and six studies, comprising 617 participants and 369 ADHD cases, reported serum iron levels. Serum ferritin levels were lower in ADHD cases (SMD = -0.40, 95% CI = -0.66 to -0.14). However, we found no correlation between serum iron levels and ADHD (SMD = -0.026, 95% CI = -0.29 to 0.24). Meta-regression analysis indicated that publication year, age, gender, sample size, and Hb levels did not significantly influence the pooled estimates of serum ferritin.

Conclusion: Lower serum ferritin rather than serum iron is associated with ADHD in children.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. The flow diagram of the selection process.
Fig 2
Fig 2. Forest plot for the random-effects meta-analysis of serum ferritin levels in persons with ADHD and controls.
Fig 3
Fig 3. Forest plot for the random-effects meta-analysis of serum iron levels in persons with ADHD and controls.
Fig 4
Fig 4. Galbraith radial plot graph of included studies.
Fig 5
Fig 5
Funnel plot for publication bias test between-group meta-analysis (A) on serum ferritin levels (B) on serum iron levels.
See this image and copyright information in PMC

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