Paranoia and mistrust: Epidemiological, Experimental, and Clinical Investigations

Paranoia entails the core rigid and unfounded belief that other people are intentionally trying to harm the integrity of the believer. This belief system is better conceptualized as a continuum, with ordinary social evaluative concerns at the end of the spectrum and hypervigilance as well as persecutory feelings at the other end. Several psychological models have been developed throughout the last decades to explore the underlying mechanisms of paranoia. Insecure attachment styles as well as negative self-esteem have been proposed as potential candidates for better explaining paranoid interpretations. However, the role of key interpersonal aspects such as mistrust has been less studied. Given the social nature of paranoid beliefs, this thesis aims to explore the role of different features of mistrust and its relationship with paranoid beliefs in non-clinical and clinical samples by employing epidemiological, experimental, and psychophysiological designs. To begin, the first chapter offers a thorough narrative review of conceptualizations of paranoia and states the objectives of this thesis. Following this, the second chapter (study 1) provides results from a large representative and international sample revealing the specific association of a tendency toward mistrusting unfamiliar faces and paranoia in contrast to related constructs, such as conspiracy mentality. The third chapter (study 2) reveals the role of a bias toward mistrust between insecure attachment styles and paranoia in a large representative UK sample. Subsequently, the fourth chapter (study 3) shows using a convenience sample, that manipulating relational schemas through an evaluative conditioning task performed online did not influence trustworthiness judgments, Lastly, the fifth chapter (study 4) explores the temporal dynamics of untrustworthiness judgements in clinically paranoid and non-clinical samples using event-related-potential techniques revealing differences in face processing between the groups. The final chapter synthesises these findings and reflects on the theoretical, methodological, and clinical implications of this thesis by also discussing general limitations, strengths, and future directions.