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Title: The exploration and differentiation of early and late onset psychosis
Author: Taylor, Lisa Elaine
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2017
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Background: Schizophrenia is a heterogeneous disorder; the mean global lifetime prevalence has been reported 0.4% and point prevalence as 0.46 % (Saha, S et al 2005). It is a highly-stigmatised disorder. It is generally considered to be an illness that starts in early adult life, but a significant proportion of those with schizophrenia (around 15%) develop the disorder between the ages of 40 and 60 years. There is uncertainty whether the late onset condition is a discrete entity or lies on a continuum with early onset schizophrenia. Four sub-groups based on the stress vulnerability model have been proposed; drug related, traumatic, stress sensitivity and anxiety psychosis. A semi-structured clinical interview (SCIPS) has been developed to classify these sub-groups. Age of onset is a core characteristic of the stress sensitivity and anxiety psychoses. Stress sensitivity psychosis is regarded as an early onset disorder (under 30 years old) and anxiety psychosis a late onset psychosis (after 30 years old). Aims: This study aimed to explore the differences and similarities between the stress sensitivity and anxiety psychosis sub-groups; to see if they are discrete sub-groups which correspond to early and late onset psychoses. This study also aimed to explore psychoses with an onset between 40 and 60 years old, to differentiate this group from early onset psychosis and determine if late onset psychosis is a discrete homogenous disorder or lies on a continuum with early onset psychosis. Methodology: Participants aged 18 to 65 years old with early or late onset psychosis were recruited by convenience sampling and classified into anxiety or stress sensitivity psychosis using the SCIPS tool. Data on socio-demographic, clinical and psychological variables was analysed using two independent samples tests; t-test, Mann-Whitney U test, chi-squared and Fisher's exact test. Spearman's rank correlation coefficient was used to analyse the relationship of the variables with age. Results and conclusions: The results fail to confirm the hypothesis that stress sensitivity psychosis is an early onset disorder and anxiety psychosis is a late onset disorder. The study did not find any significant differences in any of the demographic, clinical or psychological variables between the participants classified as stress sensitivity psychosis or anxiety psychosis suggesting they are homogenous and not distinct sub-groups. The study found some significant differences between the late and early onset groups, in particular higher levels of persecution and systematization of delusions and a greater proportion of females in the late onset group. Positive correlations were found between age of onset and both thoughts of persecution and systematisation of delusions. Systematised delusions and persecutory delusions and later age of onset are characteristics of the proposed anxiety psychosis subgroup but neither are necessary in the classification scheme. The correlations therefore are not sufficient to differentiate between the anxiety and stress sensitivity subgroups. Many of the clinical and demographic results were inconsistent with the existing literature on early and late onset psychosis. The late onset group had higher levels of self-serving attributional bias; no other differences in the psychological variables measured were found between the sub-groups. This study is exploratory and the findings are limited due to the small sample size; type 2 errors in the statistical analysis may have occurred. The exclusion of individuals with drug related and trauma psychosis also limits the generalizability of the results and may confound some of the findings when comparing the early and late onset groups. The results need confirming in larger studies. The results from this study failed to confirm the validity of the stress sensitivity and anxiety subgroups. This may inform future research into schizophrenia and into whether subgroups exist and if so the nature of them. The validity of the SCIPS tool has not been confirmed and requires further evaluation if there is to be further exploration and revision of the subgroups it has been developed to classify participants into. This exploratory study demonstrates the proposed subgroups are not valid alternatives to the current classification system. The positive and negative findings relating to the age of onset of psychosis may contribute to the knowledge base of schizophrenia and the psychotic disorders.
Supervisor: Kingdon, David ; Hansen, Lars Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available