Visual Hallucinations in Psychosis: Developing a theoretical model for future treatments.

Background: Visual hallucinations (VH) are reported by one in three people with psychosis. They are associated with poorer functioning. Despite such detrimental impact, there are no current proven effective treatments for these. This thesis reports a program of work that develops the psychological understanding and treatments of VH in psychosis.

Aims: Specific aims were to i) gain a rich understanding of the phenomenology and appraisals of VH, ii) develop an outcome measure of visions, and iii) develop a theoretical model of contributory factors and test their associations to identify future treatment targets.

Methods: People with lived experience were consulted throughout the research. First,
reflexive thematic analysis was used to explore the first-person phenomenology and
appraisals of VH in twelve people with psychosis (Chapters 2 and 3). Next, a cross-sectional study was conducted with both clinical (404 people with psychosis) and non-clinical participants (N=696) who experienced VH within the last month. This was used to undertake a psychometric evaluation and factor analysis of a new measure of VH (Chapter 4). Finally, a theoretical model of maintenance factors of VH is presented (Chapter 5). Structural equation modelling was employed to statistically test the associations of the proposed model.

Results: People with psychosis often see VH of people, who behaved like and looked like
people (Chapter 2). People lacked convincing and acceptable explanations for such complex experiences (Chapter 3). The outcome measure was psychometrically robust and is suitable for use as a brief self-report outcome measure of VH (Chapter 4). Finally in the SEM, nightmares, other hallucinations, low self-esteem, and worry significantly predicted visions (Chapter 5).

Conclusions: VH are overlooked and under explored, despite being some of the most complex, vivid, and distressing experiences reported by people with psychosis. Four maintenance factors of VH were identified, which can be targeted in future treatments.