We don't know if a person's consciousness cease to exist if their brain is destroyed because no one has ever come back from the dead.
So at best, for your position that the brain and consciousness are separate, we can say that there is absolutely no evidence for it. All current evidence points to them being one in the same.
I don't understand what you mean by "addiction has well know physical causes". That doesn't change the fact that your brain is craving something that consciously do not want.
Some people do desire the object of the addition. For instance. I do love coffee and I know I have a caffeine addiction. I have no issue with caffeine and like it.
So, again, at best, you can say that some people have a physical addition that they don't want. That still in no way implies that consciousness exists outside of a physical body.