[Thesis]. Manchester, UK: The University of Manchester; 2015.
This thesis explored the role of negative perseverative processing in psychosis. The
specific aims were twofold: to provide a contemporary, critical overview of the evidence
for the role of worry and rumination in positive psychotic symptomatology, and to
experimentally test the link between rumination and voice-hearing experiences. Paper
one reports on a systematic review of the literature; collating, synthesising and
critically evaluating the current literature relating to the associations between
worry and rumination, and psychosis. A rigorous, theoretically-driven search produced
27 papers, the findings of which indicated a varied evidence base supporting a role
for both worry and rumination in positive symptoms. A simple group-difference meta-analysis
confirmed the importance of this line of enquiry, demonstrating that worry and rumination
are higher in groups experiencing psychosis. Studies comprised a range of designs,
populations and targets of investigation, offering insight into links with delusions,
hallucinations and positive symptomatology more generally. The strongest evidence
emerged for the links between worry and paranoia, with more and higher quality papers;
although, support was also shown for links with rumination. Evaluating the field as
a whole, a number of limitations were identified, including the preponderance of cross-sectional
designs thus limiting inferences of causality and a relative dearth of research concerning
rumination, despite similar theoretical drivers for its relevance. Paper two aimed
to remedy aspects of these limitations, seeking to counter the largely cross-sectional
body of work with a rigorous experimental test of the role of rumination in voice-hearing.
Based on a continuum account of psychosis, previous evidence of feasibility and pragmatic
practicalities, a student sample was recruited. The experimental design explored whether
rumination following stressful film material resulted in a greater degree of auditory-hallucination
type experiences, given anomalous perceptual information. Differences in distress,
thematic convergence with the film content and state paranoia were also inspected.
Randomly allocated to conditions, participants were instructed to either ruminate
on the contents of a film depicting interpersonal violence, or distract themselves.
The manipulation was successful with the former group exhibiting more perseverative
thought. However, this was not accompanied by a significantly greater number of hallucination-type
experiences, or level of distress. In the context of previous evidence, the work presented
here seems to suggest that rumination might be more pertinently involved in the maintenance
of distressing psychotic experiences, rather than their initial development. This
is an important novel finding, which will guide future research efforts and provide
information to target tailored intervention efforts appropriately.