Interoception and Positive Symptoms in Schizophrenia

Abstract

The present study focuses on the multifaceted concept of self-disturbance in schizophrenia, adding knowledge about a not yet investigated aspect, which is the interoceptive accuracy. Starting from the assumption that interoceptive accuracy requires an intact sense of self, which otherwise was proved to be altered in schizophrenia, the aim of the present study was to explore interoceptive accuracy in a group of schizophrenia patients, compared to healthy controls. Furthermore, the possible association between interoceptive accuracy and patients' positive and negative symptomatology was assessed. To pursue these goals, a group of 23 schizophrenia patients and a group of 23 healthy controls performed a heartbeat perception task. Patients' symptomatology was assessed by means of the Positive and Negative Syndrome Scale (PANSS). Results demonstrated significantly lower interoceptive accuracy in schizophrenia patients compared to healthy controls. This difference was not accounted for participants' age, BMI, anxiety levels, and heart rate. Furthermore, patients' illness severity, attention and pharmacological treatment did not influence their interoceptive accuracy levels. Interestingly, a strong positive relation between interoceptive accuracy and positive symptoms severity, especially Grandiosity, was found. The present results demonstrate for the first time that interoceptive accuracy is altered in schizophrenia. Furthermore, they prove a specific association between interoceptive accuracy and positive symptomatology, suggesting that the symptom Grandiosity might be protective against an altered basic sense of self in patients characterized by higher sensibility to their inner bodily sensations.

Keywords: basic self; bodily self; grandiosity; interoception; interoceptive accuracy; positive symptoms; schizophrenia; selfhood.

FIGURE 1

Interoceptive accuracy marginal means for SCZ and HC participants. Covariates included in the model were estimated equal to the following values: age = 32.7778; BMI = 23.8401; STAI-I score = 40.6889; HR = 81.4887 SCZ: Schizophrenia patients; HC: Healthy controls. Error bars represent SE. ^∗p < 0.05.

FIGURE 2

(A) Correlation plot of the relation between interoceptive accuracy and PANSS Positive Symptoms Scale score for SCZ participants. (B) Correlation plot of the relation between interoceptive accuracy and PANSS Negative Symptoms Scale score for SCZ participants. ^∗ = Bonferroni corrected p < 0.025.

FIGURE 3

Correlation plot of the relation between interoceptive accuracy and P5-Grandiosity positive symptom for SCZ participants. ^∗p value near to the Bonferroni corrected threshold (p < 0.007).