Exposure to parabens and other endocrine-disrupting chemicals (EDCs) during adolescence may be associated with ADHD behaviors according to a study recently published in JAMA Network Open.
Phthalates, parabens, phenols, and triclocarban are found in personal care products (soap, cosmetics), plastics, packaged food, and pharmaceuticals. Although previous studies have reported associations between prenatal and early childhood exposure to these chemicals and attention-deficit/hyperactivity disorder (ADHD)-like behaviors, few have examined exposure during adolescence. Because adolescence is a critical time for brain development, exposure could be especially problematic, the researchers hypothesized.
The study authors analyzed data from the New Bedford Cohort, a prospective birth cohort of mothers and infants recruited at a New Bedford, Massachusetts, hospital between 1993 and 1998. Participants in the cohort received a 15-year follow up to assess chemical exposure.
The researchers invited the participants evaluated in the last half of the study to provide spot urine samples both during neurodevelopmental assessments as well as about 1 week later (mean duration of time after assessment, 7 days [range, 1-35 days]).
Of the adolescents invited to provide a urine sample, 81% provided at least 1 sample. Of the 144 adolescents who provided two samples, 60 had each sample analyzed separately with the mean concentration used. The remaining 84 had equal volumes of 2 samples pooled for analysis.
Because people are exposed to multiple chemicals, the researchers “created summary exposure measures by combining biomarker concentrations for chemicals with a shared mechanism of action, exposure pathway, or chemical class.”
ADHD behaviors were evaluated using checklists from the Behavior Assessment System for Children, Second Edition (BASC-2; parent-, teacher-, and self-reported) and the Conners Attention Deficit Scale (CADS; parent- and teacher-reported).
Of the 205 adolescents in this analysis, 82 (40%) scored consistently with a significant behavioral problem as defined by the assessments, while 39 (19%) had an ADHD diagnosis. That’s higher than the population estimate, which is about 10%.
Chemicals assessed have short elimination half-lives and short-term variability in exposure. Given the cross-sectional design, there is a possibility of reverse causation. Excluding participants with an ADHD diagnosis enhanced existing associations.
“Our results support the importance of adolescent exposure to EDCs, particularly phthalates, as a potential risk factor for significant ADHD-related behavior problems,” the study authors concluded.
Shoaff JR, Coull B, Weuve J, et al. Association of exposure to endocrine-disrupting chemicals during adolescence with attention-deficit/hyperactivity disorder-related behaviors. [published online August 28, 2020]. JAMA Netw Open. doi: 10.1001/jamanetworkopen.2020.15041