Adolescent exposure to endocrine-disrupting chemicals linked to ADHD-related behaviors

Exposure to endocrine-disrupting chemicals, particularly phthalates, was linked to ADHD-related behaviors among adolescents, according to results of a cross-sectional analysis published in JAMA Network Open.

“There is growing evidence that exposure to endocrine-disrupting chemicals (EDCs), such as phthalates and phenols, may be associated with ADHD,” Jessica R. Shoaff, PhD, of the Channing Division of Network Medicine at Harvard Medical School, and colleagues wrote. “Phthalates and phenols are widely used in consumer products, including food processing and packaging equipment, personal care products (e.g., cosmetics and fragrances) and pharmaceuticals, resulting in ubiquitous exposure. Although epidemiologic studies have reported associations between prenatal and early childhood exposure to EDCs and ADHD-like behaviors, few studies have examined the association of exposure to these chemicals during adolescence with ADHD-like behaviors.”

Exposure to EDCs during adolescence may be particularly harmful because of this period’s critical brain development, much of which is associated with functional and structural changes in the brain in addition to the onset of behavioral problems, the latter of which appears to be caused by hormonal changes. Shoaff and colleagues sought to determine whether adolescent EDC exposure played a role in the development of ADHD-related behaviors. The investigators collected data of 205 adolescents who were included in the ongoing prospective birth cohort, the New Bedford Cohort. Participants underwent neurodevelopmental testing and provided spot urine samples. Shoaff and colleagues performed statistical analyses using a repeated-measures analysis with multivariate modified Poisson models to approximate the adjusted relative risk for ADHD-related behaviors linked to EDC exposure. They quantified urinary biomarker concentrations of EDCs or their metabolites, such as paraben, phenols, phthalates and triclocarban, and created summary exposure measures that combined biomarker concentrations of chemicals with a shared chemical class, mechanism of action or exposure pathway. Further, the researchers assessed ADHD-related behaviors featuring up to 14 indices from self-, parent- and teacher-completed behavioral checklist using the Conners Attention Deficit Scale and the Behavior Assessment System for Children, Second Edition. They dichotomized scores on each index to identify participants who exhibited a significant behavioral problem, which was defined by the interpretive guidelines of each scale.

Results showed 82 (40%) participants had scores representative of a significant behavioral problem, and 39 (19%) had an ADHD diagnosis. Each two-fold increase in the sum of antiandrogenic phthalate concentrations was linked to a 1.34 (95% CI, 1-1.79) increase in risk for significant behavior problems related to ADHD. Moreover, each two-fold increase in the sum of dichlorophenols was linked to a 1.15 (95% CI, 1.01-1.32) increased risk. Male participants tended to exhibit stronger associations, but the researchers noted impreciseness regarding sex-specific differences.

“The identification of modifiable risk factors for ADHD is of great public health importance,” they wrote. “These findings contribute new insights into the potential detrimental neurobehavioral outcomes of EDC exposure during adolescence.”