It is my belief that Professor Drusilla is rather enjoying suffering from schizophrenia, she clearly hears voices and appears to think they come from her doll Miss Edith as she often has conversations with her, which do not appear to be one sided for her. She also seems to have a split personality (one of the symptoms of Schizophrenia) as one moment she appears to be very calm and dreamy while the next she can appear violent and threatening (this could also be caused by other mental disorders that cause mood swings). I would also suggest she is delusional though the reasons I have to back this up are pretty much the same as the ones given for schizophrenia. To give a proper diagnosis however I would have to spend more time with her in different situtaions which I really don’t want to do!