Could you share a little context how that was diagnosed? Like what's the bar for "low dopamine" with ADHD being identified as root cause? What type of doctor w

Could you share a little context how that was diagnosed? Like what's the bar for "low dopamine" with ADHD being identified as root cause? What type of doctor would do such a diagnosis? Asking as I identify with the symptoms, but no idea where to start to check them.