A number of studies have found that iron deficiency in children and adolescents is associated with lower scores of cognitive tests. Moreover, there is some evidence that iron deficiency during infancy has persistent effects on cognition that are still evident in adolescence. This may be exacerbated for those with poor family conditions.
While iron deficiency was once presumed to exert most of its deleterious effects only if it reached the level of anemia, it has more recently become recognized that many organs show negative changes in functioning before there is any drop in iron hemoglobin concentration. A large U.S. national study found iron deficiency in 3% of children (6-16), and 8.7% of girls aged 12 to 16.
There has been less research done on the effects of iron deficiency on cognition in adults, but there are indications that iron deficiency is associated with poorer attention and working memory in both young and older women.