Group-Based Brief Behavioral Therapy for Insomnia for Patients With Chronic Mental Illness

The goal of this clinical trial is to evaluate the effectiveness of a short-term, group-based Brief Behavioral Therapy for Insomnia (BBTI) intervention in chronic psychiatric patients at a hospital day ward.The main questions it aims to answer are: 1. Does the BBTI-based group intervention improve subjective sleep quality and reduce the severity of insomnia? 2. Does the intervention have a positive effect on psychological well-being and cardiometabolic/physical functions? Researchers will compare an experimental group to a waitlist control group to see if the intervention improves sleep quality, reduces insomnia-perpetuating behaviors, and enhances overall health status across various timeframes. Participants will: 1. Attend four sessions that cover sleep structure education, relaxation techniques (including acupressure), sleep-promoting diet principles, and the proper use of sedative-hypnotic medications. 2. Write a daily sleep diary. 3. Complete three times of structured self-report questionnaires. 4. Undergo physiological and physical function assessments.