The paper’s authors ran falsification tests using 58 other disorders instead of goitre to check their identification strategy, providing reassurance on the causal claim.

Evidence

Did iodized salt raise the IQ of 50 million Americans by 15 points? (Giving What We Can)

Categorization

• corroborated: 2 independent passages support this claim
• XREF: connects to: Iodizing salt in 1924 closed a 15-point IQ gap cheaply

Related

• Adding iodine to salt in 1924 raised average U.S. IQ scores (similarity 0.90)
• Salt iodization raised IQ scores of millions of people by 15 IQ points in iodine-deficient regions and is highly cost-effective at pennies per person per year. (similarity 0.88)
• Adding iodine to salt beginning in 1924 increased IQ in America by as much as 15 points and boosted the U.S. economy. (similarity 0.87)
• Americans gained up to 15 IQ points after iodized salt became mandatory in 1924. (similarity 0.87)
• A 2017 study found that the introduction of iodized salt in 1924 raised IQ for the one-quarter of the population most deficient in iodine. (similarity 0.85)
• Men from the lowest-iodine areas born in 1924 or later had an average IQ that was 15 points higher than their predecessors. (similarity 0.85)
• Iodized salt raised IQs by a full standard deviation (15 points) in iodine-deficient areas, and may explain a decade’s worth of the Flynn effect. (similarity 0.85)
• Introduction of iodized salt increased IQ by approximately 15 points for those most deficient in iodine. (similarity 0.85)
• Results are consistent with iodization raising IQ by 15 points in iodine-deficient areas and a nationwide average increase of ~3.5 IQ points. (similarity 0.85)
• Salt iodization beginning in 1924 raised IQ by approximately one standard deviation (15 points) for the quarter of the population most deficient in iodine. (similarity 0.85)
• A randomized trial in Ethiopia found iodized salt raised children’s cognitive scores by only about 4 IQ points (effect size d=0.17), far below a full standard deviation. (similarity 0.84)
• The lower range of estimates is consistent with iodization raising IQ by 15 points, but also documents at least 10,000 excess deaths from iodine-induced hyperthyroidism. (similarity 0.84)
• Iodine played a substantial role in cognitive improvements across the American population in the 20th century. (similarity 0.83)
• We find that for the one quarter of the population most deficient in iodine this intervention raised IQ by approximately one standard deviation. (similarity 0.83)
• Iodine deficiency is a major unrecognized cause of lowered intelligence (similarity 0.82)