NOS1 and attention deficit-hyperactivity disorder: Abnormal dopamine system or nitric oxide system in ADHD may also contribute to abnormalities of vascular response.50, 51, 52 In the future, combination analyses with neurobiological (eg, NO/nNOS level) and genetic features (eg, NOS1‐ex1fVNTR) may help us to interpret the CBF abnormality in adults with ADHD more comprehensively.