How To Increase Dopamine Levels?

Question: I have an adult son who was recently diagnosed with ADHD. He has his Master's, played college football, and was teaching when life just became more and more difficult. He is in therapy and taking Adderall. He uptakes slowly and really struggles with the dopamine deficiency, which gives him a tough time every day. He has always eaten a very healthy diet, he exercises regularly, struggles with sleep, distraction. It was never suggested in his childhood that he was ADHD, always well behaved and appropriately social. During the difficult time each day, he says he really struggles with distractions, and nothing quite feels right, which creates an anxious feeling. I just learned from this site that Adderall can lower dopamine levels, which are already lower in ADHD people, how can we treat the lower dopamine levels?