Abstract
In this thesis we attempt to address the complex issue of the relationship between
trauma, dissociation, and psychosis. We start by providing a brief presentation of the
background to this thesis, which is followed by an outline of the main clinical aspects
and theories of psychosis. Subsequently, a broad evolutionary overview of trauma is
given within which existing influential cognitive theories of PTSD are placed. Current
models of dissociation are then reviewed and related to the view of trauma and traumatic
stress reactions previously outlined, before providing an evaluative synthesis of the
theoretical approaches and convergent conceptualisations of trauma, dissociation, and
psychosis in order to disentangle some of the plausible processes underlying their
relationship.
It was hypothesised that dissociation, occurring as a result of trauma (experience of
psychosis), plays a key role in the formation and maintenance of psychotic symptoms,
chiefly hallucinations and delusions. We used methods from experimental
psychopathology to investigate the potential role played by dissociative processes in the
disruption of the cognitive processes of attention and memory for trauma-related,
positive and neutral information in two groups of participants: 30 individuals with
psychosis and 30 matched controls. In particular, we used self-report measures of
symptomatology, recovery style, trauma-related symptoms, and dissociation, and
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employed two experimental tasks. The first was specifically devised to assess attentional
processes: a Directed Forgetting Stroop Task (DFST) performed under conditions of
divided attention. The second task was a Word-Stem Completion Task (WSCT) on
which we applied the process dissociation procedure (PDP; Jacoby, 1991) in order to
estimate the relative contribution to dissociation of implicit and explicit memory.
As expected, our findings revealed that compared to controls the experimental group
processed information preferentially in an implicit manner, and that this effect was
predicted by levels of dissociation and trauma-related distress. Although enhanced
unconscious memory was not specific to trauma-related material, it significantly
contributed to the level of positive symptomatology when mediated by stress levels. In
contrast, the contribution of recovery style in the maintenance of psychotic symptoms
was not supported, although this may reflect a limitation of the self-report measures
employed in our study. Contrary to what was hypothesised, we did not find a standard
directed forgetting effect in our memory task or an advantage (less interference due to
dissociation) in our task of divided attention.
Results are discussed in the light of the theoretical background, previous experimental
literature, methodological limitations, and current models of trauma and dissociation
