The results of a new federal analysis were drawn from studies conducted in other countries, where drinking water contains more fluoride than in the United States.

A rigorous nine-year research review looking at the relationship between fluoride and intelligence in children concludes that as fluoride levels rise, IQ drops.

A review of 74 medical studies links higher fluoride exposure to lower IQ in kids — but mostly draws on research that took place outside of the U.S. and had a high risk of biased results. Why it matters: The federally funded analysis could further stoke the debate over adding fluoride to drinking water as Robert F.

A new report that analyzes research on fluoride and IQ scores finds that the more fluoride a child is exposed to, the lower he or she tends to score on intelligence tests. The findings' relevance to the U.

Fluoride in drinking water was associated with reduced IQ scores at levels of less than 4 milligrams per liter, but not at less than 1.5 mg/L, according to the analysis by researchers at the National Institute of Environmental Health Sciences.

Inverse associations are observed between fluoride measurements in urine and drinking water and children's IQ, according to a review published online Jan. 6 in JAMA Pediatrics, although these findings are challenged in an accompanying editorial.