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A recent ecological study found a statistically significant association of attention deficit hyperactivity disorder (ADHD) prevalence in youth with exposure to fluoride in fluoridated water. However, it included only household income as a possible covariate. In contrast another study found a significant association of ADHD prevalence with residential altitude. A multiple regression analysis including water fluoridation extent, mean US state elevation and a number of possibly important social factors as covariates showed statistically significant associations of ADHD prevalence in 2011 with altitude and per capita personal income in 2009. There was no statistically significant association of ADHD with the exposure to fluoride when these covariates were included. The ADHD-fluoridation study suffers from insufficient consideration of possible risk-modifying factors but has been widely cited because its reported findings appear advantageous to political campaigns against community water fluoridation.