If I understood it right, you can think of it like this. The drug messes with your serotonin system and you are kinda left chasing that 'high' from the drug forever, so your brain now has messed up serotonin wiring. Dopamine, another feel-good hormone, can be used to make the person feel better though.
The thing is, dopamine works on a reward (pleasure) seeking behaviour. So if you become overly dependent on it, it can be harmful as stated in the dialogue in this chapter.
Ngl Seungmin here feels like Jaeyoung's serotonin replacement to me in a way. His calmness and consistency in caring for Jaeyoung, slow and steady steps towards possible recovery if at all, that's where he plays an important role in ensuring this dopamine redirection is carried out well.
I see!! Tysm for explaining, i think i have a better understanding on how it works now!
I lwk dont get it…can some please explain the part abt the drugs and dopamine and stuff? And how seungmin affects jaeyoung too regarding that aspect