In the sensitivity test, the insignificant meta-analysis result became significant, and the children with ADHD had a significantly lower level of serum transferrin than those without ADHD after removing the subjects who received methylphenidate in the study by Menegassi, M. (2010) (Hedges’ g = −0.494, 95% CI = −0.828 to −0.160, p = 0.004)36. This evidence concerns the gene TF and attention deficit-hyperactivity disorder.