Well, I'm not a doctor but the ability of the human body and mind to heal are mind boggling. I was mostly a drinker but I did dabble in acid, shrooms and barbituates. I did honestly feel there were effects from that acid for years, although it was never very serious.
Have you tried NA or any other kind of counseling? I don't really know anything about the synthetic stuff (I'm an old fogey, that stuff is too new for me!
), but maybe in the section of SR about drug abuse?