“Iodine and Adult IQ Meta-Analysis”, 2012-02-29 (; backlinks):
Iodine improves IQ in fetuses; adults as well? A meta-analysis of relevant studies says no.
Iodization is one of the great success stories of public health intervention: iodizing salt costs pennies per ton, but as demonstrated in randomized & natural experiments, prevents goiters, cretinism, and can boost population IQs by a fraction of a standard deviation in the most iodine-deficient populations.
These experiments are typically done on pregnant women, and results suggest that the benefits of iodization diminish throughout the trimesters of a pregnancy. So does iodization benefit normal healthy adults, potentially even ones in relatively iodine-sufficient Western countries?
Compiling existing post-natal iodization studies which use cognitive tests, I find that—outliers aside—the benefit appears to be nearly zero, and so likely it does not help normal healthy adults, particularly in Western adults.