Psychometric validation of the schizotypal personality questionnaire-brief in a Japanese community sample

Schizotypal personality disorder (SPD) is increasingly important in research on schizophrenia, and the Schizotypal Personality Questionnaire-Brief (SPQB) is one of the most widely used assessment scales for evaluating the presence and severity of SPD symptoms. However, there has not been sufficient research into the psychometric properties of the SPQ-B using a large sample size, nor has there been sufficient validation of its models, such as the bifactor model. It is therefore necessary to further clarify the properties, validity, and reliability of the SPQ-B and its models.

A total of 6632 Japanese adult participants aged 20 to 59 were given the SPQB. This occurred first to set a baseline and again at a two-week follow-up. Structural validity was confirmed by confirmatory factor analysis. The smallest detectable change (SDC) was calculated at the individual and group levels.

The results suggested that the SPQ-B's bifactor model (the general factor of SPD symptoms and three group factors consisting of Cognitive-Perceptual, Interpersonal and Disorganized symptoms) had the best fit index. The individual and group SDCs were 8.19 (37.23 %) and 0.14 (0.64 %), respectively.

This study used a large sample size of Japanese adults to provide evidence for the validity and reliability of the SPQB, as well as the best fit of its bifactor model. The results not only indicated the appropriate use of the SPQ-B in clinical and research settings but will also pave the way for future research into both SPD and schizophrenia.