Iron deficiency and educational achievement in Thailand.

This double-blind clinical trial was conducted in Thailand to assess the impact of iron treatment on the IQ and educational attainment of 1358 9-11-y-old children. The children were classified into one of three groups: iron replete, iron depleted, and iron-deficient anemic. The Raven Progressive Matrices was used to measure IQ. A Thai language and a math test were administered to assess school attainment. A 50-mg/d tablet of ferrous sulphate was given for 2 wk and a 100 mg/d tablet, for 14 wk. An anthelminthic drug was given on the day of the blood test before treatment and 3 mo after the intervention started. There is evidence of a positive association between iron status and IQ and a language school achievement test but there is no support for the internal validity of the hypothesis that this association is causal.