Date of Award
Doctor of Philosophy
The purpose of this investigation was to examine a proposed two-factor model of schizophrenic symptomatology (Nicholson & Neufeld, in press). To achieve this aim, a semi-structured interview was administered to one hundred schizophrenic patients and a series of symptomatology scales were rated. Preliminary analysis indicated that these ratings were consistent with previous research in schizophrenia.;The item-level data from the scales was clustered to reduce redundancies in the large amount of data (95 schizophrenia variables) and 26 symptom clusters resulted. These symptom clusters were then rated and subsequently placed into four schizophrenia variable groups (paranoid, nonparanoid, positive, and negative). The four variable groups were put through a series of consistency tests to determine if their symptom clusters were related empirically as well as theoretically. The symptom clusters were then kept in a variable group if they met both types of relations.;Each of these variable groups were analyzed with Maximum Covariance Analysis to determine if they measured a single underlying construct. The resultant graphs were consistent with a dimensional model for the four groups. There was also some additional support for the dimensional model from comparisons of mathematically-independent categorical-model-based methods of calculating base rate estimates.;The divisions of symptoms into paranoid-nonparanoid as well as positive-negative offered strong support for the continuum of severity of disorder when they were combined. First, there was a large overlap between the two previously-hypothesized sets of divisions. Second, the four variable groups all had Maximum Covariance Analysis results consistent with latent dimensional models. If the four groups were linked, then a single dimension of disorder would result.;These findings have significant implications for both future research and clinical practice. In particular, they offer strong support for a Bleulerian view of schizophrenia as a unified whole which has different presentations. As a result, research need not become primarily concerned with trying to explain differences between groups of schizophrenia patients but should look for commonalities amongst them. Also, the increasing recognition of the importance of dimensions in diagnosing mental disorders is discussed.
Nicholson, Ian R., "The Classification Of The Schizophrenias According To Symptomatology: A Two-factor Model" (1993). Digitized Theses. 2235.