Nandrolones have quite an obvious effect on the dopamine system, serotonin system, GABA - glutamate, etc. I wont post all the stuff it does, but you can read a quick summary of it's effects
here. Some of the changes can be permanent and it definitely will effect your mental state, far after you've ceased using it. Some may notice this more, some less, some not at all but it's definitely present. And some changes can be permanent. It's effects are much more pronounced then dht's or test analogs.
I felt crazy good on it. For me, feeling wise, it's better then dbol. But me being familiar with antidepressants, anxyolitics (benzos, etc.), coke, amph's, psychedelics, etc. I know how to spot dopaminergic effects of drugs and differentiate them from other ones; serotonergic, GABAergic, etc. NPP got me really worried, as feeling this good meant it's doing a lot, and the PCT form that cycle was the hardest one to date, psychologically and physically. I take better care of my brain now. It's what my psychiatrist always talked about when mentioning aas. He's more of a neurobiologist/psychiatrist, and always confirms that aas have a strong and lasting effect on mood, cognition, depression, etc. ie. they mess with your brain chemistry. And in the case of nandrolones, this is a lot more pronounced. In any case, me personally, I am not taking NPP ever again, just bc I prefer keeping my brain chemistry as healthy as possible.