Fluoride exposure and internalizing symptoms in adolescents in a United States cohort

Abstract

BACKGROUND AND AIM: Studies have shown a relationship between early chronic, low-level fluoride exposure and attention-deficit hyperactivity disorder and learning abilities in children. Animal studies suggest a link between fluoride exposure and internalizing behaviors. No human studies have examined the impact of fluoride on internalizing behaviors during adolescence. METHODS: Participants enrolled in the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS) provided non-fasting spot urine samples at age 12 (n=286). Urine samples were analyzed using a microdiffusion method to determine childhood urinary fluoride (CUF) concentrations. Caregivers of CCAAPS participants completed the Behavior Assessment System for Children-2 at the age 12 study visit to assess symptoms of anxiety, depression, and somatization in their children. Race, age of the child, household income, maternal age at birth, caregiver depression, caregiver-child relationships, and age 12-year serum cotinine levels were considered covariates in linear regression models. Sex-specific effects of fluoride exposures were investigated through the inclusion of interaction terms. RESULTS:We observed a positive, significant association between CUF concentrations and increased somatization (β = 3.64, 95% CI 0.49, 6.81) and a positive, but not statistically significant, association with the internalizing composite scale (β = 2.64, 95% CI -0.15, 5.44). Significant sex differences were also observed; compared to females, males with higher CUF levels exhibited a greater degree of internalizing (pinteraction=0.04) and somatization behaviors (pinteraction=0.02). No associations between urinary fluoride levels and depressive symptoms were found. CONCLUSIONS:This is the first study to examine fluoride concentrations in urine collected during adolescence and internalizing symptoms, specifically somatization, with males being more at risk. Somatization straddles the interface between physical and psychological health and is often comorbid with anxiety and depression. This was a cross-sectional study; therefore, continued follow-up will help shed light on the impact of fluoride exposure on mental health in children. KEYWORDS: children’s environmental health, fluoride, mental health outcomes