The role of white noise speech illusions in indicating risk for psychotic disorders

Psychotic experiences can be measured in both heathy and ill individuals. The white noise task is an experimental paradigm, developed to elicit psychotic experiences in the form of auditory illusions. The white noise task distinguishes the non-clinical population from patients. In the present study, the white noise paradigm was used to examine to what degree speech illusions reflect individual differences in risk of psychotic disorders beyond case–control differences. Although speech illusions in the general population cross-sectionally are characterised by reduced alpha activity during a noise fragment, baseline EEG oscillatory activity did not show any association with the expression of speech illusions at the follow-up of the same sample. In addition, the analyses showed that there were no associations between white noise speech illusions and self-reported psychotic experiences or known risk factors in the general population. However, speech illusions could serve as a marker in the healthy siblings of patients with psychotic disorders, but only if they already showed high levels of trait-like risks. While the white noise task might not serve as a marker of risk for psychotic disorders, white noise speech illusions might reflect expression of the psychosis exophenotype. This thesis makes a substantial contribution to the understanding of psychotic experiences.