For instance Bleuler in 1908 claimed the disease was an organic brain deterioration and thus incurable and introduced the term schizophrenia to replace dementia praecox (Phillips & Ketelsen, 2003). Dementia praecox, according to Kraepelin, was "the young becoming old before their time" (Phillips & Ketelsen, p. 25, 2003). .
Though it appeared logical and helpful to cluster the many symptoms of schizophrenia in an accurate and useable form, nosology changed with new information about the disorder. For instance, an influential German psychiatrist Kurt Schneider, who practiced earlier in this century, clustered essential features of schizophrenia criteria into "first rank" and "second rank" symptoms (Marrin, 1995). Based primarily on observation, first rank symptoms were seen as what appeared most commonly, but second rank symptoms could also suggest a diagnosis as well (Kaplan, Sadock, & Grebb, 1994). One hundred years later the issue is still evolving. A further subdivision based on empirical evidence was described by Nancy Andreasen. She compiled a list of symptoms based on 111 schizophrenia patients and measured the percentage of positive and negative symptoms for each (Andreasen, 1987). Results for negative symptoms include; affective flattening, alogia, avolition-apathy, anhedonia-asociality and attention and results for positive symptoms were; hallucinations, delusions, bizarre behaviour and positive formal thought disorder (see Schizophrenia Bulletin, 1987, vol 18, page 9 for a complete listing). Andreasen later subdivided the positive symptoms into two groups, psychotic and disorganised dimensions (Andreasen, Arndt, Alliger et al., 1995).
The above two investigations justify usefulness in grouping symptoms, but the criteria have changed. For instance, behavioural aspects of schizophrenia observed by Schneider were reorganised by a research team headed by Andreasen. She used differential statistics to group the symptoms that loaded with each other, in terms of treatment and research responses.
