Hello, I Was Told By A Friend Who Was Not

hello,
I was told by a friend who was not aware of what i have been going threw, but who is studying medicine (how it came up in conversation) that some people can not ever fully recover emotionally from long term use of oxycodone do to the fact that are brain or body stopped producing the chemical that can make us happy because the drug was in control or something of that sort. I guess i am asking is there a chance that my body will never again be able to produce the chemical that makes me happy? or in other words is there a chance that I will never again be able to feel real happiness like i did before the drug because I destroyed that part of me by abusing the drug for so long?