Paraben and Phthalate Exposure in Adolescents With Attention-Deficit/Hyperactivity Disorder: A Case-Control Study

This case-control study compared urinary concentrations of parabens and phthalate metabolites between adolescents with attention-deficit/hyperactivity disorder (ADHD) and healthy peers and examined whether product-use behaviors accounted for observed exposure differences.

Adolescents aged 12-17 years with clinically diagnosed ADHD (n=39) and age- and sex-matched healthy controls (n=41) were recruited. Urinary concentrations of seven parabens and ten phthalate metabolites were quantified using validated high-performance liquid chromatography and gas chromatography-mass spectrometry protocols. ADHD symptoms were assessed using Conners Parent and Adolescent Rating Scales. Group comparisons were conducted using t-tests with effect sizes (Cohen's d). Multivariable logistic regression, factorial analysis of covariance (ANCOVA) models (reporting partial η²), and multiple mediation analyses were performed, adjusting for household income, parental education, and body mass index.

Differences in the urinary concentrations of several parabens and phthalate metabolites were observed between adolescents with ADHD and controls. However, detection frequencies varied across analytes, and findings for compounds with low detection frequency should be interpreted with caution. In multivariable logistic regression, an association between dimethyl phthalate and ADHD status was observed (odds ratio=6.13; 95% confidence interval, 1.10-34.34), with improved model discrimination (Δχ²=17.2, p=0.002; area under the receiver operating characteristic curve, 0.856→0.921); however, this finding should be interpreted with caution given its low detection frequency. In ANCOVA models adjusting for product-use behaviors, group differences remained significant only for dimethyl phthalate (F(1, 71)=7.97, p=0.006, η²=0.099); however, this finding should likewise be interpreted with caution due to its low detection frequency. Mediation analyses indicated that recent personal care product use did not substantially mediate the association between ADHD status and chemical exposure levels.

Adolescents with ADHD showed differences in internal exposure to selected parabens and phthalate metabolites. These findings should be interpreted with caution, particularly for analytes with low detection frequency. Overall, these findings suggest that exposure differences may reflect behavior-linked vulnerability patterns during adolescence rather than short-term cosmetic use alone. Longitudinal studies are needed to clarify temporal and causal pathways.