The purpose of this study was to assess the reliability and validity of the Thai version of the CDSS for the evaluation of depression in patients with schizophrenia.

Sixty patients with schizophrenia according to DSM-IV-TR were recruited in the study. The Thai version of CDSS, the Mongomery and Asberg Depression Scale (MADRS), the Hamilton Depression Rating Scale, 17-item version (HDRS-17), and the Positive and Negative Syndrome Scale (PANSS) were administered. Major depressive episode diagnosed by a psychiatrist according to the DSM-IV-TR was used as a gold-standard.

The internal consistency of the Thai version of CDSS was very good (Cronbach’s alpha = 0.869). The inter-rater reliability was found to be in substantial agreement with the intra-class correlation coefficient (ICC) of 0.979. The test-retest reliability over a period of three days was high, with the ICC of 0.861. The Thai version of CDSS showed significant correlations with the MADRS (r =0.887), the HDRS-17 (r=0.865) and the PANSS-G6 (r=0.833). The areas under the ROC curves of the CDSS, MADRS, HDRS-17, and PANSS-G6 against the DSM-IV-TR criteria for major depressive episode were 0.993, 0.954, 0.966, and 0.933, respectively. The optimal cut-off scores to discriminate between depressed and nondepressed patients was 6/7, with a sensitivity of 92.31% and specificity of 97.87%.

The Thai version of CDSS is a reliable and valid measure for the evaluation of depression in Thai patients with schizophrenia.