An Investigation of the Psychometric Properties of Illness Perception Questionnaire for Schizophrenia (IPQS) in Iran

Abstract

The present study has been carried out in order to evaluate psychometric characteristics of Illness Perception Questionnaire for Schizophrenia. This is a descriptive correlational research. The study population consisted of all patients with schizophrenia aging 19 to 70 years old who were hospitalized in the Psychiatric Ward of Shafa Hospital, Rasht (2016). Out of this population, a sample size of 95 people was obtained using purposive sampling, Demographic Questionnaire, Illness Perception Questionnaire for Schizophrenia (IPQS), Positive and Negative symptoms Scale (PNSS), Scale to Assess Unawareness in Mental Disorder (SUMD), Beck Depression Inventory (BDI), and Calgary Depression Scale for Schizophrenia (CDSS). Exploratory factor analysis revealed that this questionnaire is composed of 10 dimensions, the first of which explaining 24.402 percent of all of variance. Besides, concurrent validity showed that the total IPQS score had a significant correlation with SUMD equal to 0.579 at the level of 1 percent; this correlation was 0.29 at the level of 5 percent and 0.615 at the level of 1 percent in relation to BDI and CDSS, respectively. However, no correlation was observed between IPQS score and PANSS. Cronbach's alpha coefficients of reliability for IPQS scale were 0.705, and, for the subscales, between 0.599 and 0.865. This result suggests a good reliability for the Illness Perception Questionnaire for Schizophrenia. The Illness Perception Questionnaire for Schizophrenia has helpful psychometric properties that make it an appropriate analysis tool.