Non-Psychotic Traits of Schizophrenia as Abnormalities of Cerebral Asymmetry: Development of a Potential Early Screening Instrument

Schizophrenia;Sense of Self in Schizophrenia;Early Screening Instrument for Schizophrenia;Cerebral Asymmetry in Schizophrenia;Early Intervention tool in Schizophrenia;Non-Psychotic trait abnormalities

Ball, Kate Louise ; Miller, Robert

University of Otago

关键词: Schizophrenia;    Sense of Self in Schizophrenia;    Early Screening Instrument for Schizophrenia;    Cerebral Asymmetry in Schizophrenia;    Early Intervention tool in Schizophrenia;    Non-Psychotic trait abnormalities;   

Others  :  https://ourarchive.otago.ac.nz/bitstream/10523/1658/1/BallKateL2010PhD.pdf

美国|英语

来源: Otago University Research Archive

【 摘 要 】

The main aim of this research is to provide the basis for future development of an early screening instrument to identify individuals who may be at risk of developing schizophrenia (or related disorders). It is based on a neurodynamic theory of schizophrenia (Miller, 2008) which accounts for the non-psychotic trait abnormalities that are characteristic of the disorder. These abnormalities are enduring traits present before, during and after a psychotic episode and may become manifest in teenage years. Hence there is a potential to use these traits to identify risk at this stage for the purpose of intervening early with supportive, and/or educative resources to guide at-risk individuals to utilise their potential strengths, and help with the inevitable challenges that such a disorder may bring. The theory is based on a premise that there is a relative absence of rapidly conducting cortico-cortical axons thought to be associated with functions normally preferred by the right hemisphere. Most functions (but not all), that signify a trait abnormality in schizophrenia, come into this category. This suggests that schizophrenia has homogenous origins that manifest in a number of different impairments. The traits correspond broadly to two cortical states, the ;;upstate’ and the ;;downstate’. They were resolved further into 16 ;;a priori’ subject areas of function. These a priori categories were assessed in an instrument (the Schizophrenia Traits Questionnaire, or STQ), consisting of 96 statements about everyday experiences, to be rated on a 5-point Likert scale. In order to test the theory as the basis for a potential early screening instrument, it was necessary to test the large-scale correlational structure of the 96 items deriving from it, using Factor analysis. A second aim was to assess whether the 16 a priori categories could reliably distinguish schizophrenia and normal. The third aim was to find the combination of the items in the STQ which can best predict whether an individual will fall into the schizophrenia group or normal group with a high level of accuracy. Two versions of the STQ (;;STQ1’ AND ;;STQ2’) were tested on 300 mental health users (MHU) and 300 non-mental health users (non-MHU). There was some overlap in respondents from STQ1 to STQ2 (40 identified in the MHU group). For both STQ1 AND STQ2, factor analysis involved a 2-step process (due to the requirements of factor analysis for 5-10 respondents per item). Step 1 consisted of 16 separate factor analyses from which 26 factors emerged overall. Summary scores of the 150 MHU and 150 non-MHU participants on each factor, were used for the second step in a Grand Factor Analysis to assess the overall conceptual structure. Both step 1 and step 2 of the factor analyses supported the underlying theory. Power analyses were performed on each item in STQ1 to determine how many respondents were needed for the comparison t-tests to have ;;power’ (to reject the null hypothesis). Paired t-tests were performed on all 96 items of STQ1 to compare MHU and non-MHU participants. 30 items were eliminated from STQ1 on the basis of 5 criteria. 1.Item loading above 0.400 on its factor 2. P-value (in relation to T value) ≤0.05; 3. Number of subjects needed for comparison from power calculations for each item, 4. Conceptual coherency, 5. Specificity and relevance to the underlying theory. On the basis of this process, items in STQ1were changed and refined in developing STQ2. Consent to seek a verified diagnosis (including some associated information: see appendix 1c) was given by 136/150 MHUs. 75/136 had a verified diagnosis of schizophrenia. Factor analysis was performed on STQ2 and gave the underlying theory further support. The results support the corresponding 2 factors (of ;;disorganisation’ and ;;psychomotor poverty’) of Liddle’s (1987) 3-factor classification of the symptoms of chronic schizophrenia. Paired t-tests were then performed on the 75 schizophrenia respondents matched to 75 normal respondents for age, sex and number of years at secondary school. These comparisons revealed statistically significant differences between groups in 56 of the STQ2 items, with no items giving significant challenge to the theory. Paired t-tests were also performed on a smaller group of 29 with a verified diagnosis of unipolar depression and 29 matched with schizophrenia and also 8 with diagnoses of bipolar disorder matched with 8 with schizophrenia. This was for the purpose of distinguishing statistically between schizophrenia and other mental health groups to eliminate the possibility that traits are associated with mental health users in general rather than schizophrenia in particular. Reliability statistics (kappa) were performed on 62 repeat (normal respondents) over a 6 to 12 month period. Using the results of the factor analyses, t-tests and kappa statistics, groups of items were chosen to perform a Discriminant Function Analysis on 75 schizophrenia respondents and 150 normal respondents. A combination of 13 items was able to predict whether an individual would fall into the schizophrenia or normal group to 85% accuracy. Strengths that stand out from other early intervention instruments are: (1) The STQ is based on a psychobiological theory backed by empirical evidence (2) The theory defines trait abnormalities that can be independently assessed by questionnaire (3) The traits are enduring and not dependent on prodromal symptoms but on everyday activities enabling earlier detection (4) STQ is easily administered, inexpensive, with innocuous items potentially suited to young people (5) Thirteen of the items in combination accurately predicted schizophrenia to 85% accuracy in this sample with no mention of psychotic symptoms. In studying the theoretical background to the STQ, it was possible to link it to a previous work of the author (Smith 1998) on the sense of self in schizophrenia. It is therefore suggested that there is an imbalance in a ;;now experiencing I’ and an ;;objectified me’ in schizophrenia. There is justification for this, given that in schizophrenia there is difficulty in the self interacting in the moment as subject, until experience can be conceptualised and the self becomes object (to itself). This ;;I/me’ split has been further realised in the current work on trait abnormality: The functions normally preferred by the right hemisphere coincide with the function of the ;;I’ as the ;;subject’ of experience, which is impaired in a manner similar to other trait abnormalities. The strength of the conceptualising left hemisphere to compensate for impairment in the right corresponds to the ;;me’ as ;;object’ (and to a trait that is potentially better than normal in schizophrenia, the tendency to ;;long trains of thought’). Points are raised in regard to the ;;gap’ between the analysis of psychological or brain mechanisms and ;;whole person psychology’, which corresponds to the psychiatrist’s world of hard science while dealing with human beings, and the philosophical dilemma of mechanism versus meaning.