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What Causes What
MECHANISM+ INCREASES

Ferritin → Cognitive performance

Higher Ferritin increases Cognitive performance.

Treating iron deficiency in young women can move attention and memory on named tasks. Murray-Kolb and Beard (2007) showed that in a blinded 16-week trial. Two later trials in the same age band again find the gain where ferritin rose. Berglund's infant trial found no WISC-IV difference at age 7.

Randomized trial · Moderate

Supported by an experiment or a tightly identified design. Read the caveats.

Mechanism

Murray-Kolb and Beard (2007) gave women aged 18 to 35 either 60 mg of iron a day or a placebo for 16 weeks. One hundred forty-nine sat eight tasks from Detterman's Cognitive Abilities Test at the start. One hundred thirteen came back. Iron-sufficient women were more accurate and faster than women with iron-deficiency anemia. Women who were iron-deficient but not anemic sat in between. After treatment, a rise in serum ferritin tracked a five- to seven-fold gain in task accuracy. A rise in hemoglobin tracked speed. Iron is a cofactor in dopamine synthesis and in myelination. That is the pathway the authors point to. The identified object is leaving a deficit. Climbing a normal ferritin is a different claim. Blanton (2014) assigned 43 young women to beef or non-beef lunches, 85 grams, three times a week, for 16 weeks. Both lunches raised body iron. The lunch type did not move cognition in a consistent way. Seventeen women whose ferritin rose gained more on planning speed (One Touch Stockings of Cambridge), spatial working memory strategy, and sustained attention (Rapid Visual Information Processing) than the 26 whose ferritin did not. Food iron still belongs here because the measure is iron stores. Leonard, Chalmers, Collins, and Patterson (2015) ran a pilot. Twenty-four women with latent iron deficiency (ferritin at or below 20 μg/L and hemoglobin above 120 g/L) were randomized to placebo, 60 mg, or 80 mg of iron for 16 weeks. Eight iron-sufficient women took placebo. On the IntegNeuro battery, women whose plasma ferritin rose gained more on Impulsivity and Attention than women whose ferritin did not. The authors say a powered trial would need 26 to 84 women in each iron group. Berglund and colleagues (2019) randomized 285 marginally low-birth-weight infants (2,000 to 2,500 g) to 0, 1, or 2 mg/kg/day of iron from 6 weeks to 6 months. At age 7, 205 sat the WISC-IV. The abstract reports no significant differences between arms on that scale.

Caveats

These are young women, mostly students. They are not executives with a wellness panel. Excess iron is a different clinical object. Do not read this as high ferritin making leaders. Murray-Kolb's accuracy claim is a ferritin-responder analysis inside a randomized trial. Hemoglobin responders got speed, not accuracy. Blanton's randomization was beef versus non-beef, and that contrast failed. The cognition signal sits in who raised ferritin. Verbal free recall went the other way. Blanton treats that as likely an artifact. Forty-three women finished. Leonard is a pilot. Twenty-five women finished. Iron-deficient and iron-sufficient women did not differ at baseline on the IntegNeuro domains. The randomized treatment contrast reached significance on Impulsivity, not on the full battery. Ferritin improvers versus non-improvers is a post-hoc split. The authors asked for a larger trial. Two later trials do not make the first one more settled. They are small, and one is a pilot. Berglund is low-birth-weight infants followed to age 7, not the young-women deficiency trial. Two hundred five of 285 were assessed. WISC-IV and the Five-to-Fifteen questionnaire did not differ by iron dose. Child Behavior Checklist externalizing scores favored the supplemented children. That is behavior, not this pair. A fourth paper does not make Murray-Kolb more settled.

Effect

qualitative. Leaving iron deficiency improved named tasks in young women. A food trial and a pilot again tie the gain to a ferritin rise. Berglund 2019: LBW infants, WISC-IV at 7 not different by iron dose.

Nodes

Biology & endocrinologyFerritinPsychology & behaviorCognitive performance

Named confounders

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What Causes What. “Ferritin → Cognitive performance.” https://whatcauseswhat.org/edges/e-ferritin-cognition (atlas updated 2026-09-02).

https://whatcauseswhat.org/edges/e-ferritin-cognition

Papers