Yep, interestingly, both involve dopamine irregularities, but in different directions. ADHD people have lower dopamine baseline in the prefrontal cortex (leading to inattention). Stutterers have been shown to have excess dopamine in the basal ganglia (leading to over-blocking of speech movements). That’s why ADHD meds boost dopamine in the prefrontal cortex, and dopamine antagonists (Ecopipam, Pagoclone, Abilify, Risperidone etc) block or down regulate dopamine in the basal ganglia, which helps stutterers (without ADHD) with fluency.