Date of Award

2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Abstract

Schizophrenia is an often-debilitating mental illness whose etiology remains unknown, although a number of conceptualizations have been suggested. Among the most prominent of these conceptualizations is the diathesis-stress model, which posits that liability to the disorder is genetically mediated, although ultimate expression is dependent upon exposure to various environmental stressors. Meehl (1962) is arguably most responsible for this conceptualization of schizophrenia. Identifying those who are liable for schizophrenia has the potential to inform treatment which may lead to better outcomes. In an effort to better understand the developmental process of schizophrenia and to identify those who may be at increased risk for the disorder, researchers have shifted their attention to the study of endophenotypes, including neurocognitive indicators. Another endophenotype of increasing interest to researchers is premorbid personality indicators. Using assessment measures such as the Chapman Psychosis Proneness Scales (CPPS; Chapman, Chapman & Raulin, 1978; Eckblad & Chapman, 1983; Eckblad, Chapman, Chapman, & Mishlove, 1982) and Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher et al., 1989), evidence has been found that suggests the presence of certain premorbid personality indicators may be indicative of a liability to schizophrenia. The present study examined what organization of personality indicators, as determined using the MMPI-2, can best identify those who may be liable for developing schizophrenia. Those having liability for schizophrenia (hypothetically psychosis prone; HPP) were identified by scores on the CPPS, and compared to a matched comparison (MC) sample. It was hypothesized that significant group differences would exist on all MMPI-2 scales of interest; this was largely confirmed. It was also hypothesized that specific MMPI-2 scales would successfully discriminate between the HPP and MC groups; this was confirmed. Additionally, this study sought to determine if the Personality Disorder Interview-IV (PDI-IV; Widiger et al., 1995), Personality Disorder Questionnaire-4 (PDQ-4; Hyler, 1994), and Wechsler Adult Intelligence Scale-IV (WAIS-IV; Wechsler, 2008a, 2008b) could be helpful in identifying those who may be liable for developing schizophrenia. It was hypothesized that significant group differences would exist in the personality disorder domains of interest on the PDI-IV and PDQ-4; this was confirmed. Additionally, it was hypothesized that all the personality disorder domains of interest on the PDI-IV and PDQ-4 would be correlated; this was again confirmed. Finally, it was hypothesized that the WAIS-IV subtests of Digit Span (DS), Arithmetic (AR), and Coding (CD) would evidence negative correlations with the personality disorder domains of interest, and with the MMPI-2 scales found to most successfully discriminate between the HPP and MC groups; these hypotheses were not supported. The results are in-line with previous research that has supported premorbid personality indicators as a potential endophenotype of schizophrenia, and the MMPI-2 as a measure useful in this area of research (Bolinskey & Gottesman, 2010). Additionally, the results support previous literature which has suggested schizotypy should be viewed as a multidimensional construct (Kwapil & Barrantes-Vidal, 2015). Furthermore, that all personality disorder domains of interest, and most MMPI-2 scales of interest, evidenced significant group differences suggests that abnormal personality traits should be utilized in identifying those who may have liability for schizophrenia.

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