Thank you for posting this question and topic about codependency. I just realized I have been in a relationship where I was a codependent with a sufferer. Through my self discovery and reading on this forum etc. I have learned a lot oboist this subject.
I do think that sufferers, especially those who turn to drugs and alcohol to cope, seek out and find codependent people to be dependent on. It seems that the codependent person, supporter (not to say that all supporters are codependents), feel some level of joy and purpose in taking care of the dependent, as well as feel some level of fulfillment because their caretaker nature is being fed; although this nature is in extreme.
I also think that dependents need to be justified and enabled, which only an unhealthy relationship of dependency and codependency will support.
Not that this applies to all sufferers and supporters, I do think that PTSD is a breeding ground for this type of relationship.
I have never been in a relationship of this type in the past, but this summer I believe I was. I am an extremely forgiving, understanding, and care taking type of person. I would not have gone to such extremes of caring and empathy with just anyone though in my past. This changed when I met a sufferer that I wanted to love and be loved by. I discovered that he is an alcoholic, he then began abusing drugs this summer, and was relying on me, using me, to feel better about himself and be taken care of. At first I loved how much he needed me and wanted to be with me, but then I realized he had no coping skills. If he wasn't with me all the time, he was getting himself into trouble. He did kind and giving things for me too, so it also became a mutual codependent situation sometimes.
It got bad, really bad with lies, dependency on his part on everything including me, drugs and alcohol, and food, so bad and dangerous that I realized what was happening and got out. This wasn't meant to be about me and my situation, so I won't go on with that.
I mean to say that I have been in a dependent / codependent relationship with a sufferer, and through rewind many similar stories and other things on this topic, it does seem to me that especially within PTSD, these types of people seek each other out and find each other.