Table 2 Summary and comparison of main findings of meta-analysis about peripheral iron levels in ADHD.

Tseng PT (2017) (current MA)

May 1, 2017

22

Serum iron

Serum ferritin

Serum transferrin

No different serum iron between ADHD and control (Hedges’ g = −0.060, 95% CI = −0.268 to 0.147, p = 0.569) (HE: p = 0.002, PB: not significant) but changed to significant lower serum iron in ADHD after removal potential confounding one study (Hedges’ g = −0.186, 95% CI = −0.323 to −0.048, p = 0.008)

Lower serum ferritin in ADHD than control (Hedges’ g = −0.246, 95% CI = −0.440 to −0.051, p = 0.013) (HE: p < 0.001, PB: p = 0.426)

No different serum transferrin between ADHD and control (Hedges’ g = −0.324, 95% CI = −0.704–0.057, p = 0.096), HE: p = 0.207, PB: p = 0.587

None of the clinical variables has association

Wang Y.¹⁶

Jul 25, 2016

11

Serum ferritin

Serum iron

Lower serum ferritin in ADHD than control (SMD = −0.40, 95% CI = −0.66 to −0.14)

No difference in serum iron (SMD = −0.026, 95% CI = −0.29 to 0.24)

None of the clinical variables has association

Scassellati C.¹⁴

Sep, 2011

7

Blood ferritin

Lower blood ferritin in ADHD than control (d = −0.86, Z = 2.52, p = 0.01), HE: p < 0.001

n/d

Tan LN.¹⁵

Mar, 2011

5

Blood ferritin

Lower blood ferritin in ADHD than control (mean difference = −23.09, 95% CI = −33.06 to −13.13, Z = 4.54, p < 0.001), HE: p = 0.003, PB: N.S.

n/d