As someone who suffers from mental illness I can tell you that physicians misdiagnose people all the time. When you suffer from mental illness you often do a poor job of explaining your symptoms in the clinical terms that your physician needs to hear to make your diagnosis. Your physician may diagnose your psychotic disorder as depression or your personality disorder as schizophrenia. My personal experience with this is that I experience tactile hallucinations as formication (feeling like things are crawling beneath your skin). When I had my first mental breakdown I believed that beings from another world had somehow come into my body and I subsequently became delusional. They then gave me the diagnosis of having schizoaffective disorder and all my treatment was based on that. When I went to other hospitals they just looked at my chart and never gave my diagnosis a second thought. Had someone explained to me what formication was I would have been able to understand and explain my condition better to the physician. Instead I went through years of telling someone there are aliens inside me and there was nothing you could tell me otherwise. It wasn’t until I received a copy of the DSM-5 and was able to understand the terminology of my illness that I stopped believing there were beings in me. Only then was my physician able to see that I wasn’t suffering from delusions. It was groundbreaking because I was able to master my treatment and not suffer on the wrong medication, receiving the wrong treatment.