Nature of delusion and delusion-like belief

Delusions have been defined as false beliefs different from those that almost everyone believes. However, studies suggest that beliefs (including delusions) comprise a continuum where content does not distinguish psychosis. Despite the explicit characterisation of delusions as (false) beliefs, most research has focused on delusions while neglecting non-clinical beliefs. To address this, the first formal study of key features of belief was conducted. A large public survey (n=1000) confirmed that most regarded beliefs as relatively stable personal convictions, capable of influencing thoughts and/or behaviour. These participants then completed the Cardiff Beliefs Questionnaire (CBQ), a newly developed measure designed to investigate the prevalence of different types of belief (delusion like bizarre and non-bizarre, paranormal, religious, and societal/cultural). Results showed that 38% of participants strongly endorsed one or more delusion-like beliefs) (DLB), with 91% reporting at least one 'weak', 'moderate' or 'strong' DLB. Moreover, 26% strongly endorsed at least one bizarre DLB. Levels of DLB endorsement were not distinguishable from those of paranormal and religious beliefs (P&RB). These findings support a continuum account but present difficulties for existing clinical definitions of delusion. The CBQ also investigates anomalous experiences (AE), given their proposed causal role in delusion formation. AE and anomalous beliefs (DLB and P&RB) were associated in this sample, but the relationship was not found for all individuals, suggesting that having AE is neither necessary nor sufficient for holding anomalous beliefs. Finally, belief consistency and coherence were explored across and within different belief types. DLBs appeared less stable than other belief types, emphasising the importance of functional characteristics in distinguishing clinically relevant beliefs. In addition, while seemingly contradictory beliefs were reported by some, results generally supported coherence between DLB and P&RB. Collectively, these findings complement those of traditional clinical studies, while demonstrating the value of non-clinical investigations in elucidating the nature of delusions.EThOS - Electronic Theses Online ServiceGBUnited Kingdo