A large epidemiological study in Environmental Health has linked higher levels of exposure to fluoride in drinking water with higher ADHD rates in children and adolescents in the US. In Newsweek, a number of independent medical analysts described the findings as both plausible and important.
York University psychologists Christine Till and Ashley Malin used CDC data on state water fluoridation starting in 1992 and National Survey of Children’s Health information on prevalence of ADHD diagnoses from later years. They also controlled for the frequent impact of socioeconomic status on ADHD diagnosis rates -- though a limitation of the study was that they did not examine any individual children or individual rates of exposure.
"State prevalence of artificial water fluoridation in 1992 significantly positively predicted state prevalence of ADHD in 2003, 2007 and 2011, even after controlling for socioeconomic status," they wrote. "A multivariate regression analysis showed that after socioeconomic status was controlled each 1% increase in artificial fluoridation prevalence in 1992 was associated with approximately 67,000 to 131,000 additional ADHD diagnoses from 2003 to 2011."
“The results are plausible, and indeed meaningful,” Harvard University physician and epidemiologist Philippe Grandjean told Newsweek, adding that this and other recent studies suggested that we should “reconsider the need to add fluoride to drinking water at current levels."
Thomas Zoeller, a specialist in the study of endocrine disruptor chemicals like fluoride called the study unique and "important" and told Newsweek that, "Given the number of children in the U.S. exposed to fluoridation, it is important to follow this up.”
Water Fluoridation Linked to Higher ADHD Rates (March 10, 2015)
Malin, Ashley J., and Christine Till. “Exposure to Fluoridated Water and Attention Deficit Hyperactivity Disorder Prevalence among Children and Adolescents in the United States: An Ecological Association.” Environmental Health 14, no. 1 (February 27, 2015): 17. doi:10.1186/s12940-015-0003-1. (Abstract)