Background Mental disorders are recognized as a major cause of disability and disease burden across the lifespan. Gua Sha is believed to improve mental health and sleep quality significantly. Tui Jing is an innovative type of Gua Sha therapy that penetrates deep into the muscles and fascia rather than just acting on the surface of the skin. Modern research has revealed that Gua Sha is extensively utilized for pain-related symptoms, and its therapeutic effects may be attributed to anti-inflammatory and immunomodulatory mechanisms. Although Gua Sha has demonstrated efficacy in treating various diseases, limited research exists regarding its impact and underlying mechanisms on mental health. This study will conduct a pilot clinical trial to assess the efficacy of Tuijing Therapy on mental health. Autonomic function is closely associated with psychological symptoms, and HRV reflects the activation of the vagus nerve. This study aims to obtain preliminary evidence that Gua Sha can modulate HRV by regulating vagal function, potentially ameliorating psychological disorders.

Population A formal sample size estimation is not required for pilot feasibility studies because the primary objective of this study is to assess feasibility and acceptance. The sample size is estimated according to a method for preliminary pilot study. The researchers aim to recruit 36 participants to assess the feasibility of the study. Adults without any chronic diseases who score over 14 on the HAM-D 17 and have no smoking or drinking habits will be included.

Method A pilot randomized controlled study will be conducted with Tuijing therapy as the intervention and sham therapy as the control. The intervention group will receive the actual intervention, while the sham intervention group will undergo a sham ultrasound treatment process that does not involve the active therapeutic components. A computer-generated random allocation schedule will be complied with before commencement by a researcher not involved in recruiting participants. Tuijing therapy will be administered as arm A, while the sham control group will serve as arm B. There will be a 5-day interval between interventions. Participants in arm B will receive 6 times of sham ultrasound therapy with 30 minutes each session lasting 1 month. Participants in arm A will receive 6 times of Tui Jing therapy with 30 minutes each session lasting 1 month. Heart rate variability, brain activity, skin reflection, pain perception, psychological symptoms, and sleep quality will be assessed as outcome measures.

Outcomes The primary outcomes of this study are feasibility, acceptance, and satisfaction. As secondary outcomes, this study will assess changes in heart rate variability, brain activity, skin reflection, pain perception, psychological symptoms, and sleep quality. Heart rate variability will be measured using a heart rate variability monitoring device, sleep quality will be assessed using the Pittsburgh Sleep Quality Index (PSQI), and psychological symptoms will be evaluated using several related scales.

Procedures The researcher will conduct an initial telephone interview to provide study information and screen potential participants for eligibility. Each participant will receive full details about the study's purpose and will be required to sign an informed consent form. All participants will be invited for two in-person sessions before accepting any intervention. In the first session, comprehensive medical histories, brief semi-structured interviews for psychological symptoms, clinical examinations, general information, and questionnaires will be conducted to determine eligibility. Eligible participants in the first session will be included in the second session. The second session will be scheduled to collect baseline data for further analysis. Eligible participants meeting inclusion criteria will be randomly assigned to receive either Tui Jing therapy or sham stimulation. The intervention will be conducted by a qualified therapist (with a qualification in TCM [Master's and Bachelor's degree in Traditional Chinese medicine]) from the Department of Rehabilitation Sciences at PolyU, while another qualified researcher will be responsible for clinical interviews, screening, and data collection.

Inclusion Criteria:

• Age 18 - 55 years old
• Willingness to participate in the study and undergo randomization
• Proficiency in Chinese
• Absence of severe chronic diseases
• Experience with depression symptoms for over three months
• Scoring 20 or higher on the Montreal Cognitive Assessment (MoCA)
• Scoring above 14 on the Hamilton Depression Rating Scale 17

Exclusion Criteria:

• The presence of cardiovascular disease (CVD)
• Severe head trauma, intracranial hypertension, implanted ferromagnetic devices, or a history of epilepsy
• Engagement in any pharmacological or non-pharmacological treatments within the past month
• Existing skin conditions or susceptibility to skin injuries
• Any form of cognitive impairment

Confidentiality Agreement

Screening and baseline assessments will precede the randomization process. A computerized program will generate a randomization sequence, assigning participants in a 1:1 ratio to active or sham stimulation. To ensure concealment, opaque sealed envelopes will be used, managed by a research assistant not involved in the direct handling of the study. While it is impossible to blind the therapist due to the intervention's nature, assessors will remain unaware of the treatment assignments. To evaluate the effectiveness of the blinding, participants and assessors will be asked two questions at the study's conclusion: "What type of treatment do you believe you/the participant received?" and "How confident are you that you received active stimulation?" The latter will be rated on a scale from 0 (no confidence) to 10 (very confident), aiming to measure their perceptions and confidence regarding the treatment received.