Self-relevance of patients with schizophrenia

Abstract

Background: Delusion of reference is the most common psychotic symptoms (International Pilot Study of Schizophrenia, WHO 1973). This involves misjudgment of self-relevance nature of external information. Determination of another person’s eye gaze direction is critical in social interaction and has often been the theme of reference delusion. The current study aims at exploring the involvement of cognitive functions and psychopathology in the mechanisms of increase sense of self-relevance in patients with delusion of reference using eye-gazing task. Methods: Three groups of participants matched with age, gender and level of education were recruited. These were patients with schizophreniaspectrum disorders with delusion of reference (SAPS item 14≥4), patients matched with diagnosis and were in remission, and healthy subjects. All participants had normal or corrected-to-normal visual acuity. Patients were assessed with Scale for the Assessment of Positive Symptoms (SAPS), the Scale for the Assessment of Negative Symptoms (SANS), the Peters Delusions Inventory (PDI), the Ideas of Reference Interview Schedule (IRIS), the Beck Depression Inventory (BDI), digit span and digit symbol coding. All healthy control subjects were assessed with the same tools except SAPS and SANS. All participants performed the eye-gazing task programmed with E-prime Professional 2.0. The whole task has six blocks and each block contains 30 photographs of one model taken facing straight to camera with different gaze directions (0° and 10°,15°,20°,25° and 30° to the left and right). All stimuli was presented randomly and each lasted for 200ms, and then followed by a fixation cross until the participants respond. The next trial starts after the response of participants. The participants were instructed to decide if they had a sense of being looked at for each trial. The response accuracy and response time of participants were recorded automatically by the E-prime program. Results: Fourteen patients, nine patient control and eight healthy control participants were recruited. There were no significant differences in digit span performance among the three groups, but normal controls performed better than patients in digit symbol coding. At 10°, 15° and 30° gaze aversion, patients with active symptoms were more likely to report a sense of being looked at than healthy participants. No differences were found between patient control and healthy participants. Relationship between accuracy rate at all gaze angles and clinical and cognitive functions were analysed for all three groups. For patients, significant correlation was found between accuracy rate and PDI at gaze angle 25° (r=-0.695, p=0.006). The accuracy rates were also correlated with total score of IRIS at gaze angle 15° (r=-0.638, p=0.014) and 25° (r=-0.868, p<0.0001). Significant correlations between BDI and accuracy rates of gaze angle 15° (r=0.654, p=0.011), 25° (r=0.896, p<0.0001) and 30° (r=0.652, p=0.012) were also found. No significant relationships were found for other groups. Discussion: Patients with delusion of reference are more likely to misjudge self-relevance of ambiguous eye gazing direction. This is a valid task to demonstrate the increase sense of self-relevance in patients. Results suggested the accuracy of judgment was not relating to attention, short term memory or processing speed. Lack of correlation of symptom severity and accuracy but significant correlation with PDI and total score of IRIS suggested this state is more related to the pervasiveness of the reference idea than the severity. Relationship between BDI and accuracy suggested the importance of mood in the mechanisms of self-relevance.