You are correct. It is estimated that 40% of people with a mental illness also experience severe addiction. Within that group of "dual diagnosis" a very high percentage suffer with anosognosia- which is a neurological impairment affecting the right hemisphere of the brain which permanently impairs the person's capacity to recognize that that they have an illness.  API and its revolving door is the result of a systematic failure to recognize anosognosia and treat it as part of the illness.