Q. I have a client that I am trying to help get in touch with mental health services. He has previously been diagnosed with schizophrenia, PTSD, and borderline personality disorder. I was recently told that it isn’t possible to have both schizophrenia and borderline personality disorder. Is this true, and if so what is the reasoning?

A. I am not aware of any “rule” that says that individuals diagnosed with schizophrenia cannot be diagnosed with borderline personality disorder. Perhaps the person you learned this information from incorrectly believes that borderline personality disorder means that the individual is “bordering” between neurosis and psychosis. Under this theory, a person could not be schizophrenic because they have not crossed the psychosis threshold (i.e. their bordering between neurosis and psychosis), a required feature of a schizophrenia diagnosis. “Borderline” does not mean that an individual is teetering between neurosis and psychosis, although some believe this. People with borderline personality disorder display certain symptoms such as mood and self-image instability, difficulty engaging in relationships, anger and depression, “all or nothing thinking”, and so forth. A person with schizophrenia can display these aforementioned symptoms, in addition to psychosis, as well as some of the other symptoms of schizophrenia. The two disorders are not mutually exclusive meaning that if a person has schizophrenia, then he or she cannot be diagnosed with borderline personality disorder. From my understanding, it is possible for an individual to have both disorders simultaneously. It may be relatively rare but it’s still possible. I hope this helps. Thanks for writing.