We therefore aimed to identify the factor solution of the CRDPSS. As described elsewhere,⁴ 166 in patients with schizophrenia (diagnosed with the DSM-5),⁵ age ≥18 years and ≤65 years, and length of hospital stay ≥2 weeks were recruited in Korea. Half were men (51.5%). Their mean age and age at onset were 46.5 (SD=11.2) and 25.2 (SD=13.2) years, respectively, and the mean chlorpromazine equivalent dose of antipsychotic prescriptions was 921.1 (SD=952.0) mg.

Mean scores on the hallucinations, delusions, disorganized speech, abnormal psychomotor behaviors, negative symptoms, impaired cognition, depression and mania were 2.04 (SD=1.30), 2.27 (SD=1.16), 1.62 (SD=1.35), 1.16 (SD=1.16), 2.01 (SD=1.24), 1.22 (SD=1.22), 0.51 (SD=0.70) and 0.19 (SD= 0.48), respectively. An exploratory factor analysis (EFA) was conducted on the CRDPSS, with principle components extracted by the varimax method. The number of factor in the solution was estimated on a scree plot, using eigenvalues >1.⁶ In addition, only a loading >0.40 was considered to reveal a clear factor structure and content. As a result, Bartlett's test for sphericity was significant [χ² (166)=468.72, p<0.001], and the total variance of the factor solution was 70.69%. Table 1 gives the factor loadings for a three-factor solution. The first factor consists of the domains for delusions, hallucinations, disorganized speech and abnormal psychomotor behavior, and is designated "positive/speech". The second factor consists of the domains for negative symptoms and impaired cognition, and is named "negative/cognition". The third factor consists of the domains for depression and mania, and is designated "depression/mania". In addition, Pearson's correlations between the factor scores on the CRDPSS and the total and subscale scores on other measurement tools were obtained. Scores on the positive/speech factor were significantly correlated with scores on the positive symptoms subscale [Brief Psychiatric Rating Scale (BPRS)]⁷ (r=0.81, p<0.01), negative symptoms subscale (BPRS)⁷ (r=0.62, p<0.01), resistance subscale (BPRS)⁷ (r=0.44, p<0.01), Scale for the Assessment of Thought, Language and Communication (TLC scale)⁸ (r=0.64, p<0.01), Calgary Depression Scale for Schizophrenia (CDSS)⁹ (r=-0.32, p<0.01), Young Mania Rating Scale (YMRS)¹⁰ (r=0.58, p<0.01) and Clinical Global Impression of severity (CGI-S)¹¹ (r=0.85, p<0.01). Scores on the negative/cognition factor were correlated with scores on the negative symptoms subscale (BPRS) (r=0.35, p<0.01), resistance subscale (BPRS) (r=0.38, p<0.01), TLC scale (r=0.40, p<0.01) and CDSS (r= 0.17, p=0.03), and scores on the depression/mania factor were correlated with scores on the psychological discomfort subscale (BPRS)⁷ (r=0.25, p<0.01), the CDSS (r=0.17, p<0.01) and the YMRS (r=0.81, p<0.01).

Our investigation has the virtue of pioneering research into the evaluation of patients with schizophrenia using the CRDPSS. In summary, it shows that the 8-domain CRDSS has a three-factor structure, consisting of positive/speech, negative/cognition and depression/mania factors. Pearson's correlations indicate that all three factors have favorable concurrent and divergent validity. Hence, our findings shed light on the heterogeneous symptom components of schizophrenia.