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two major theories are currently debated as the origin of npd. one states that is a form of arrested psychological development while the other believe is a defense mechanism against psychological pain built at a young age that those mechanisms could have developed from characteristics that made the child perceive him / herself with a low self image or feel insecure are very feasible.

well everyone has issues, but in my own opinion i dont think so, it is possible, but not likely, because most narcissists were already confident to begin with and then I think they just start seeing themselves in everyone they meet like different qualities that would make them better and they just keep building on it.