Having codependent personality disorder is really destructive to both the person that they are caring for as well as themselves.
Most addicts that are suffering from one form of addiction or another cannot begin to see how destructive their behavior is because they always have someone to rescue them in a codependent situation.
It is only when people reach bottom that they begin to see the error of their ways and seek help. People with a codependency personality can prolong the addiction that a loved one is experiencing because codependent people want acceptance and they do not want the person who is addicted to be mad at them.
However, the codependent person is actually selfish here because they are putting their needs of acceptance ahead of the needs of the addictive person to heal.
It is just like a wife that is married to an alcoholic and buys the alcoholic all the alcohol that they requested. By accommodating the alcoholic the alcoholic will be happy with the codependent person but the codependent person is creating an even larger problem for the alcoholic.
This is why interventions are so powerful because the family gathers together to tell the addict why they are worried about them and this dose of reality is what the addict needs.