CALY, a neuron‐enriched transmembrane protein involved in clathrin‐mediated endocytosis and dopaminergic signaling, regulates AMPA receptor internalization, axonal trafficking, and D1 receptor dynamics[52, 67, 68, 69, 70] Dysregulation of CALY has been implicated in neuropsychiatric conditions such as ADHD and schizophrenia.[71, 72] In our study, CALY was upregulated in plasma but downregulated in patient‐derived brain organoids, suggesting compartment‐specific alterations in synaptic and dopaminergic signaling. Here, CALY is linked to attention deficit-hyperactivity disorder.