Abstract
Research consistently demonstrates how psychological factors, such as affect and cognition, can impact symptom perception. Furthermore, the way in which individuals process bodily experiences, including symptoms, can be altered or impaired and research highlights a role for alexithymia and interoception. In addition, there is also tentative evidence that some individuals may have difficulty differentiating between emotions and physical symptoms, yet this idea remains poorly understood and conceptualised. This thesis therefore used both quantitative and qualitative methods to explore the construct of Interoceptive Crossover and the perceived similarity between emotions and physical symptoms with a focus on its definition and measurement, how it relates to other constructs including alexithymia and interoception, whether it can be induced experimentally and how people make sense of their bodily sensations. The thesis consisted of four empirical studies.
Study 1 used a cross-sectional online questionnaire to develop a measure of Interoceptive Crossover (n= 239) and found that some individuals perceive physical symptoms and emotions as more similar, with certain symptom- emotion pairs more common and others more unusual and unexpected. Study 2 used a cross-sectional online questionnaire to explore how Interoceptive Crossover is related to other cognitive-affective variables previously implicated in symptom perception (n=458). The findings indicated Interoceptive Crossover was related to alexithymic and interoceptive facets and to greater levels of somatic symptom distress and trait negative affect. Study 3 used an experimental design to induce state Interoceptive Crossover and explore its impact on symptom perception, in addition to exploring the relationship between state and trait Interoceptive Crossover (n=197). Participants were randomised to one of three conditions (control vs negative mood induction vs physical symptom (pain) induction) and reported post-induction physical symptoms and emotions. State Interoceptive Crossover could be induced following induction of negative mood; however, this was not related to trait Interoceptive Crossover. Those who scored higher on trait Interoceptive Crossover reported more physical symptoms and emotions overall. Study 4 used a qualitative design (n= 12) to explore how individuals experienced and made sense of range of bodily states. The findings indicated individuals described, experienced, attended to, made sense of and communicated bodily states and symptoms and that bodily states became symptoms when they surpassed a series of thresholds unique to the individual. Overall, the thesis findings indicated Interoceptive Crossover is a discrete phenomenon, related to but distinct from other induvial differences in bodily processing, including interoception and alexithymia. Interoceptive Crossover is related to increased symptom reports and to greater levels of state and trait negative affect, suggesting it may play a role in the experience of both symptoms and emotions. This has implications for our understanding of the nature of error in symptom perception, assumptions of accuracy and validity in symptoms and our understanding of the notion of a symptom.