The impact of social and sensory stress on cognitive biases and delusions in schizophrenia.

INTRODUCTION: Stress aggravates delusional symptoms, but the exact underlying mechanisms are still not fully understood. One of the routes may be via exacerbation of information processing distortions frequently observed in psychosis. The aim of the present study was thus to investigate the impact of social and sensory stress on specific cognitive processes along with different dimensions of delusional thinking.

METHODS: Nineteen individuals affected by schizophrenia and 15 healthy controls were assessed under 3 experimental conditions (social stress, neutral, noise stress), with counter-balanced presentation of stress conditions across participants of both groups. Under each condition participants performed parallel versions of experimental tasks and had to report their level of paranoid thinking and subjective distress.

RESULTS: Irrespective of condition, patients showed significant impairments in metacognitive accuracy compared with controls. When social stress was applied first, mentalising accuracy decreased significantly in the subsequent condition among patients only. Following exposure to either social or sensory stress, patients reported significantly higher conviction in their paranoid ideas in the subsequent condition.

CONCLUSIONS: Only limited evidence was found for the negative impact of stress on cognitive processes in schizophrenia patients. However, this may not be true for those with more severe information processing abnormalities and/or delusions.