Looking for links between atopic dermatitis and ADHD

The etiology and pathophysiology of attention-deficit/hyperactivity disorder are not yet fully understood, but studies have suggested a relationship with inflammation.

To investigate further, Lena Boemanns, Julia Staab, and Thomas Meyer, from the University of Göttingen, Germany, assessed the associations between ADHD and three inflammatory conditions—atopic dermatitis, otitis media, and herpes simplex infection—and found a positive link.

In their post hoc analysis of data from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), they found a statistically significant association between peripheral inflammatory disease and the presence of ADHD.

Several mechanisms could explain a comorbidity of inflammation and the development of ADHD, the researchers say.

Several studies have already shown that IL-6 and IL-1β are associated with ADHD and ADHD-like symptoms. They cite other studies that have suggested a pathophysiological relationship with inflammation. One review of 20 studies, for instance, demonstrated a positive association between ADHD and atopic dermatitis, although it found no association between serum IgE levels and ADHD symptoms. A case–control study found that serum interleukin-6 (IL-6) levels were significantly higher in ADHD patients compared with a healthy control group.

And in a previous study of data from the KiGGS study, these authors reported “significant and inverse associations” between the prevalence of ADHD and both serum vitamin D concentration and systolic blood pressure. (In that study, they proposed that immunomodulatory effects of vitamin D might have an impact not only on the prevalence and course of autoimmune and/or infectious diseases, but also on the pathogenesis of ADHD.)

This post hoc study involved 6,922 participants (aged 11 to 17) with available data on ADHD diagnosis. According to parents’ ratings, 430 of the children and adolescents had been diagnosed with ADHD.

Atopic dermatitis was diagnosed in 1,164 participants. After adjusting for clinically relevant confounders (age, sex, BMI, socioeconomic status, migration status, mean systolic blood pressure, and 25[OH]VitD), ADHD remained a significant predictor of all three inflammatory diseases. A lifetime diagnosis of ADHD was reported more frequently in patients with atopic dermatitis (8.1% vs. 5.7%), otitis media (7.1% vs. 5.2%), and herpes simplex (7.3% vs. 5.9%) than in participants without these diseases.

To their knowledge, the researchers say, this is the first study to examine an association between ADHD and atopic dermatitis, otitis media, and herpes simplex infection using the same cohort. They acknowledge that the cross-sectional and post hoc design don’t allow for a causal interpretation for the observed association between ADHD and peripheral inflammatory diseases, as the level of evidence does not reach that of a randomized controlled trial.

“Further research is needed,” they conclude, “to unravel the physiological mechanisms underlying these associations.”