How psychosis is conceptualised shapes every aspect of how it is studied. It affects the samples it is explored within, the psychometric scales used to measure it, and the statistical paradigms used to analyse it. If this conceptual foundation is not sound, it has extensive ramifications for the validity of any insights gained from subsequent research which has been built upon it. The way in which researchers have thought about psychosis has changed a number of times over the years. It is currently widely accepted that psychotic experience is distributed along a continuum in the general population (Van Os, Hanssen, Bijl, & Ravelli, 2000). Over the last two decades, many researchers have begun to investigate subclinical forms of psychosis in order to gain a better understanding of the construct as a whole and to learn how individuals transition along the psychosis continuum (de Leede-Smith & Barkus, 2013). However, the mechanisms underlying psychosis development were found to be highly complex and difficult to unravel. As a response to these levels of complexity, in more recent years some have begun to study psychosis at the symptom level. This approach involves treating each psychotic symptom as a standalone experience and attempting to understand its specific causes and developmental trajectories before exploring how it interacts with other psychotic symptoms (Owen, O’Donovan, Thapar, & Craddock, 2011). A hallmark of psychosis which has been a popular target of examination at the symptom level is paranoia. However, the role that paranoia plays in psychosis development, especially in its early stages, remains poorly understood. Chapter 2 of this thesis explores the distribution of psychotic experiences in the general population. Results identify underlying subgroups of individuals who are XVII characterised by varying levels of psychotic experience and who appear to be at increased risk of developing psychosis. The high levels of paranoid ideation in these subgroups highlight its relevance in the general population. Chapter 3 investigates how different psychotic experiences relate to the underlying psychosis continuum. Results indicate that paranoia is closely related to this underlying continuum. Furthermore, the finding that paranoia is associated with milder levels of psychosis severity compared to other psychotic experiences indicates that it may emerge at an earlier stage of psychosis development. In chapter 4, psychotic experiences are visualised as a network of interacting events so that the nature of the relationships between them can be explored. Paranoia is found to be highly connected to all other psychotic experiences, indicating that it is a highly influential experience in relation to psychosis as a whole. Finally, in chapter 5, the temporal relationships between psychotic experiences are explored. The relationships between paranoia and other psychotic experiences are found to be reciprocal in nature, with each having the ability to predict the other’s development. This highlights the complexity of the causal relationships between these experiences. For too long, we have neglected the importance of individual psychotic experiences. This thesis suggests by exploring the associated risk, course, and outcome of these experiences, psychosis research can move beyond the limitations of potentially flawed diagnoses.
- Social factors
- Psychosis continuum