I don't think excessive masturbation itself is the only cause.
It is possible that our dopamine levels are depleted, but I think there could be some other issue somewhereelse in our body that is not allowing dopamine to be restored to his normal level.
In my case it could be because of adenoma, in other cases it could be thyroid, infections, viruses, etc...
I am saying that because analyzing my history, I have the feeling I got adenoma since I was a child given that I 've been affected by a delayed growth.
I've tried long time abstinence too, but at the end i was ejaculating regularly because of nocturnal emissions, because it's a need of our body.