## 2 Case Description and Methods
### Data Analysis  
#### 2.4.1 Quantitative Analysis  
The preliminary survey, end-of-program survey, and follow-up survey were conducted using a questionnaire. The questionnaire comprised the Impact of Event Scale-Revised (IES-R-K), which was first developed by [PERSON] in 1997 [39] and was enhanced by [PERSON] et al. in 2005 [40]. It additionally included the Athens Insomnia Scale (AIS) developed by [PERSON] et al. in 2000 [41]. The IES-R-K is a self-report scale for trauma-related symptoms. It has 22 questions. The scale is composed of five points (0 to 4), with 0 being \"not at all\" and 4 being \"a lot\". On this scale, a total score of 24 or higher indicates \"the need for clinical consideration for PTSD\", a score of 33 to 36 is a \"potential PTSD level\", and a score of 37 or higher is clinically considered to indicate \"to the extent that the immune system is not functioning properly\". On this scale, a score higher than 17-18, is considered to indicate having partial PTSD symptoms, and if 24-25 or higher, it is considered to indicate having full PTSD symptoms [40]. The full PTSD assessment can be classified in detail as follows: a score of 25-39 is moderate PTSD, 40-59 is severe PTSD, and 60 or higher is very severe PTSD [42]. The AIS comprises eight questions to evaluate the quantity and quality of sleep. This scale has four score points for each question (0 to 3), with 0 being \"no problem at all\" and 3 being \"very serious\". This scale is used to make a clinical judgment on the degree of sleep disorder using the sum of scores. If the total score is less than 4, it is deemed \"maintaining a good sleep state.\" If it is between 4 and 5, it is \"doubtful insomnia\", and if it is 6 or more, it is considered that an \"insomnia test is required\". The subject wore the heart rate sensor, which measured the peak-to-peak interval (r-r' interval) during each intervention session with a Bluetooth-based communication application. The sensor was worn on the subject's chest according to the manufacturer's guidelines [43]. During psychotherapy, the application obtained the subject's heart rate information and calculated the HRV in real time. After psychotherapy, the HRV was calculated using the Open Source Python Toolbox for HRV [44; 45]. Among the various components of HRV, the root mean square of successive RR interval differences (RMSSD), the standard deviation of the NN intervals (SDNN), the absolute power of the very-low-frequency band (VLF, 0.00-0.04 Hz), the absolute power of the low-frequency band (LF, 0.04-0.15 Hz), the absolute power of the high-frequency band (HF, 0.15-0.40 Hz), and the ratio of the LF-to-HF power (Ratio) were calculated and compared [44; 45; 46]. The calculation equations for the RMSSSD and SDNN are as follows [46]:  
\[RMSSD =\sqrt{\frac{1}{N-1}{\sum_{i=1}^{N}}{\left({RR_{i+1}-RR_{i}}\right)^{2}}} \tag{1}\] \[SDNN =\sqrt{\frac{1}{N-1}{\sum_{i=1}^{N}}{\left({NN_{i}-\overline{NN}} \right)^{2}}} \tag{2}\]  
where N is the number of measured values, RR is the time between two detected heartbeats, and NN is the time between two filtered heartbeats. The initial 3-min data for each session were discarded as artifacts. The HRV indexes neurocoradiac function and is generated by heart-brain interactions and dynamic non-linear ANS processes [46]. The HRV is an emergent property of interdependent regulatory systems, which operate on different time scales to help us adapt to environmental and psychological challenges [46]. Higher values of RMSSSD and SDNN signify higher top-down self-regulation (the ability to regulate behavioral, cognitive, and emotional processes) [47]. The change ratio of the HRV was assessed as well to check the subject's current state. The RMSSD and SDNN in this investigation were calculated using the measured heartbeat intervals for the latest five minutes. The RMSSD at minute 18 was calculated using the recorded heartbeat intervals from minute 13 to minute 18.