Soft neurological signs in schizophrenia

• Main Author: Chen, Eric Y. H.
• Published: University of Edinburgh 2004
• Subjects: 616.89
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642788

This dissertation describes a series of studies addressing the prevalence, correlates and longitudinal changes in soft neurological signs (SNS) in schizophrenia. SNS are found to be increased in schizophrenia. The increase appeared to have both a genetic and a non-genetic component. It has been proposed that SNS could be considered as one of the biological markers expressing a mediating risk for schizophrenia. In order to clarify the role of SNS in this perspective it is important to understand factors that affect the expression of SNS in a given population. Previous studies have identified possible relationships between SNS on one hand, and age, ethnicity, intelligence as well as education levels on the other. Associations with clinical features as well as cognitive function impairment have also been suggested. Antipsychotic medication side-effects appear not to be directly related to SNS, nevertheless their impacts cannot be entirely ruled out. Inconsistencies have also emerged as a result of sampling and methodological variations. The potential change of SNS with time in different phases of the disorder is another important issue that has not been adequately addressed with longitudinal studies. This dissertation describes works that addressed some of these issues in different samples using the same assessment methodology. A relatively extensive cross-sectional study addresses the relationship of SNS with demographic, educational, clinical and cognitive factors. The level of SNS in a Chinese sample is also compared with that obtained in a Caucasian sample to investigate effects of ethnicity. Data from the cross-sectional study also allow a limited analysis addressing the contributions of age and illness duration across a wider time range. Two longitudinal studies then focus on specific phases of the disorder. The first study investigates changes in SNS amongst chronic patients approaching old age (the fifth decade). The second study addresses changes in SNS following first episode psychosis. In the first chapter a broad introduction to methodological issues is presented. Chapter 2 continues with a more detailed review of the existing data about SNS in schizophrenia. Chapter 3 presents the core methodology and assessment instruments used in the studies. In Chapter 4 the recruitment procedures and the characteristics of the samples are described. Data analysis and results are presented in Chapters 5 to 8. In Chapter 5 important correlates of SNS are explored using data from a larger crosssectional sample of Chinese patients and controls. These include age, gender, education level, intelligence, as well as symptom correlates of SNS. The potential effects of ethnicity were further explored by comparison between Chinese and Caucasian control samples. Additional analyses were carried out to attempt to address the relative importance of age and illness duration for SNS in patients. Chapter 6 describes in more detail the relationship between SNS and cognitive functions in this cross-sectional sample. Chapters 7 and 8 describe two longitudinal studies. Chapter 7 deals with a 3-year follow-up study for stable chronic patients. Chapter 8 addresses a 2-year follow-up study of SNS in first episode patients. In Chapter 9 the dissertation ends with a general discussion of the current findings and suggestions for key areas for future research.