In continuing analysis of the interplay between inflammatory cells, Claudin-5 levels, and ADHD symptom severity, in our study, neutrophils show a positive association with Claudin-5 levels, which may act to protect the integrity of the BBB via an increase in the Claudin-5 expression in the TJs of the endothelium of the BBB. Here, CLDN5 is linked to attention deficit-hyperactivity disorder.