Well you are talking about two different issues. First of all, psychological and Freudian theories are now considered outdated as regards psychiatric disabilities (my prefered term for mental illness). That doesn't mean people with psychiatric disabilities don't experience normal feelings that need psychotherapy. And there are complex issues. The dissociation I experience is neurological in origin but the way it expresses itself is because of the traumatic experinces I have experienced as a child (being that my primary disability, schizoaffective disorder is in recovery and I don't experience standard psychosis). For a person with borderline personality disorder, however, part of the cause of it is a traumatic childhood experience. And for ptsd, a person would not have acquired it otherwise but the traumatic experiences caused brain changes. And people would say psychiatry isn't up on the exact chemical mechanisms of the brain but the experimental treatment for schizoaffective I am on targets the receptors in an exact manner and the genetic studies of schizophrenia proved this. Of course the psychotic thoughts I had before recovery were about my own particular fears. They all differ.
To summarize for effective treatment medication and talk therapy work together to help a person recover.