Characterising the Impact of Sleep Loss on Cognitive-Affective Processes Underlying Psychotic Symptoms

Abstract

Psychosis is the presence of hallucinations and paranoia, and has been shown to co-occur with sleep disturbances such as insomnia or poor quality sleep. Recently, it has been shown that sleep disturbances may precede the emergence of the symptoms of psychosis and occur prior to diagnosis of a psychosis disorder. However, it is still uncertain what links disturbances in sleep with the symptoms of psychosis including paranoia and hallucinations. There are considerable overlaps in the cognitive-affective consequences of sleep loss and the mechanisms of, in particular, paranoia. Therefore, we explored the explanatory power of these overlapping mechanisms to further understand the pathway from sleep disturbance to paranoia. We focused on a non-clinical sample in line with the continuum approach to psychosis in order to understand sleep disturbances prior to a formal diagnosis. Chapter one provided an overview of the literature for both sleep disturbances and psychosis which highlighted an overlap between these two distinct literatures. This chapter also identified a causal link between sleep and paranoia, and highlighted promising mechanisms of this link which had yet to be tested. Chapter two expanded on this with a formal systematic review, complemented with effect sizes, to examine the evidence for a causal association between sleep disturbances and psychotic-like, dissociative and hypomanic experiences. Research which addressed putative mechanisms was also highlighted and a research agenda was established. Chapter three started by examining cross-sectional and longitudinal putative mediators of the link between insomnia and paranoid ideation in a sample recruited online. This study supported the role of negative affect and emotion regulation as cross-sectional mediators. However, a longitudinal relationship between insomnia and paranoia was not found when baseline symptoms were controlled for. This prevented a formal examination of longitudinal putative mediators. Based on the identification of negative affect and emotion dysregulation as significant mediators in chapter three, we used experience sampling methodology, with sleep tracking, to explore these further in chapter four. We studied the effect of sleep loss on daily paranoia and putative mediators identified in previous chapters. A significant relationship was found between previous night sleep duration and next paranoia scores. This study also identified that emotion dysregulation and dissociation, but not negative affect, were significant mediators of this link. In chapter five we explored a causal relationship between sleep disturbances, paranoia and putative mechanisms through an experimental sleep deprivation design. We found that a single night of at-home sleep deprivation was associated with increases in paranoia, but not hallucinations. The significant effect for paranoia was only found for retrospective measures but not for momentary assessments of paranoia. This discrepancy provided a possible explanation for previous failures to produce an increase in paranoia following experimental sleep deprivation. In respect to putative mechanisms, emotion dysregulation was shown to increase following sleep deprivation but other cognitive and affective mechanism did not show a significant change. Finally, chapter six brought together all of these findings and placed them in light of the wider literature on sleep and psychosis. The implications of emotion dysregulation as a putative mechanisms explaining the link between sleep disturbances and paranoia was addressed, and the findings were appraised in light of the overall strengths and limitations of the thesis. Clinical implications and future research was considered.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Gillian Haddock (Supervisor) & Filippo Varese (Supervisor)