PER2 and attention deficit-hyperactivity disorder: Corroborating prior findings (Coogan et al. 2019; Faltraco et al. 2021a, b, c), dexamethasone-induced synchronization in HDFs from individuals with ADHD and control subjects elicited rhythmic expression of key circadian genes, including BMAL1, CRY1, PER2, and PER3. No statistically significant differences between groups were found in the analyses.