Are the Insomnia Severity Index and Pittsburgh Sleep Quality Index valid outcome measures for Cognitive Behavioral Therapy for Insomnia? Inquiry from the perspective of response shifts and longitudinal measurement invariance in their Chinese versions

The purpose of this study was to examine whether the Insomnia Severity Index (ISI) and Pittsburgh Sleep Quality Index (PSQI) are valid outcome measures for Cognitive Behavioral Therapy for Insomnia (CBT-I). Specifically, we tested whether the factorial parameters of the ISI and the PSQI could remain invariant against CBT-I, which is a prerequisite to using their change scores as an unbiased measure of the treatment outcome of CBT-I.

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