## 6 Conclusions  
Virtual reality provides a novel way of treating anxiety disorders in immersive environments. The subjects are gradually exposed to several levels and scenarios of traumatic stimuli (virtually), which complies with the systematic desensitization principle. The advantage of VRET is that it solves the problem of patients avoiding fear situations in traditional treatment and reduces the risk of physical injury for patients. Furthermore, the exposure intensity and time duration can be adjusted and the treatment can be terminated immediately to stop a panic attack. In addition, VRET can be used for treatment at more flexible times and allow patients to repeat specific scenes until they master their fears. The equipment is designed so that it is more convenient for doctors to monitor the patients' physical and mental condition during ET treatment. The research refines and verifies the VRET design, development, and experiment for driving phobia treatment. The experiment examined whether the TG subjects' distresses were reduced after VRET and showed that fears of driving were effectively reduced. A survey of 121 subjects used a median split to create two groups: one high on fear of driving and one low on fear of driving. The two groups were \(t\)-tested as being significantly different in fear levels. From the sixty with a relatively high fear of driving, 30 were randomly selected while waiting in queue as the TG to participate in the VRET experiment. The 30 subjects in the TG provided biofeedback during VRET treatments for analysis. At the end of the experiment, the subjects in TG were asked to fill out the same self-measurement driving behavior survey. According to survey results, there was significant post-treatment improvement. The fears of driving were reduced to the same levels as drivers in CG (i.e., their anxious driving and anxiety-related-avoidance behaviors had no significant differences). In the research, the immersive experience of VRET also showed significant improvement as indicated in the biofeedback data analyses. In conclusion, the survey results and the data demonstrate the effectiveness of VRET for driving phobia treatment. Although significant progress has been made with VRET treatments in this research, driving phobias and other PTSDs are still far from satisfactory treatment. For future research, the development of an intelligent VRET that is customized with customized treatment programs based on individual patient's fear is a challenging direction. While conducting the experiment, the subjects' degrees of fears can be monitored and analyzed simultaneously and constantly with advances in computing technology. Thus, a self-adaptive smart VRET system that automatically adjusts the exposure therapy to ensure safe and effective customized treatment is the future research goal. A.T., project administrator, construct the research framework, and incorporated VR and biosensor technologies; C.V.T., PTSD, anxiety disorders, exposure therapy literature overview, and interpretation of data analysis; C.-M.C., subject evaluation, PTSD, OCD, and PD theories, clinical ET design, and IRB application; M.-C.T., subject evaluation, ET design review, and IRB application; R.R.T.K., VRET implementation, statistical analysis, and system integration; A.P.C.L., literature review, prototype testing, and data analysis. All authors have read and agreed on the published version of the manuscript. This research is partially supported by the joint research grant of National Tsing Hua University, Chang Gong Memorial Hospital, Taoyuan General Hospital, Ministry of Health and Welfare, and the individual research grants of Ministry of Science and Technology, Taiwan (Grant numbers: MOST-108-2221-E-007-075-MY3 and MOST-108-2410-H-009-025-MY2). This clinical experiment design was thoroughly reviewed and approval by the Chang Gung Medical Foundation (CGMF) Institution Review Board (IRB) and its ethical commission. The approval number is 201901262B0.