In support of the above findings, DKK1, an antagonist of Wnt signaling, exhibited rhythmic expression in both ADHD and control groups in our study, with a delayed phase shift observed in ADHD cells, similar to BMAL1 and CRY1. Furthermore, DKK3 exhibited rhythmic expression exclusively in ADHD cells. Here, DKK1 is linked to attention deficit-hyperactivity disorder.