More than 50 million people worldwide have experienced physical trauma as a result of a traffic accident [1]. Traffic accidents are a major cause of posttraumatic stress disorder (PTSD) and serious physical damage. PTSD is a psychological reaction to a traumatic event characterized by avoidance, hyperarousal, and numbness [2,3]. In addition, PTSD can lead to a variety of mental symptoms in severe cases, along with persistent negative emotional states such as helplessness, guilt, anger, and fear. Exposure-response prevention (ERP) is an effective approach for treating PTSD and is regarded as the first-line treatment for PTSD according to numerous guidelines [4,5].

Exposure therapy is based on the theory of emotional processing [4]. Taking a traffic accident situation as an example, the patient should be repeatedly and intentionally exposed to such situations for a prolonged period in the treatment setting for s successful therapeutic outcome. However, as it is obviously not possible to expose the patient to a traffic accident situation in the hospital, the therapist instructs the patient to imagine an accident. Unfortunately, this is difficult to achieve because many patients have problems visualizing traumatic events in detail [6]. In addition, some patients may not remember the accident that they were involved in.

Virtual reality exposure therapy (VRET) is a promising treatment for patients with trauma and stress related disorder (Supplementary Table 1, available online). The underlying mechanism of VRET can be explained by emotion processing theory and/or inhibitory learning theory because it is presented as a stimulus by digitally embodying a traumatic situation (Fig. 1) [4,7]. The advantages of VRET over image exposure have been repeatedly described [8,9]. However, empirical literature on the therapeutic effects of VRET is lacking, and it is necessary to discuss the appropriateness and stability of virtual reality (VR) as a therapeutic modality. New research is needed to refine and update VRET. In this study, we report two cases treated using VRET, and discuss the effectiveness of VR for presenting anxiety-provoking stimuli.

The VRET that we developed combines VR with an existing treatment for PTSD called prolonged exposure (PE). The patient is exposed to computer graphics, sounds, and other sensory input in real-time to create a metaverse. Compared to the existing PE approach, which exposes the patient through their imagination, exposure through VR evokes greater sensory stimulation in a planned manner. Our VR program reconstructs the traffic accident experienced by the patient through a pre-evaluation process, and determines the stimulus intensity that they can endure via a questionnaire (Fig. 2). The driving scenario was specifically designed for this study and adapted to the patient’s accident situation. The therapist can customize the driving place, road width, weather, accident time, type and color of the car according to the participant’s report. In addition, the therapist controls the intensity and frequency of the VR stimuli. Participants experience the VR environment through a head-mounted display running a driving simulator (a 360° 3-dimensional video). The wheels and pedals do not have actual driving control functions.

Our VRET was based on a treatment manual that we developed previously. Figure 3 provides a detailed overview of the 6-week treatment program. Each 20−30-minute session consisted of psychoeducation, cognitive therapy, a “stabilization technique”, and exposure to a VR traffic accident. The VR part was repeated three times per treatment session (total of 90 seconds per session [~5 minutes over the entire program]). The short exposure time was used to minimize cybersickness caused by VR. After exposure, the patient provided a subjective unit of distress (SUD) score during a 60-minute session with a therapist. During that session, the therapist helped the patient frame the traumatic accident in a new way by working with their memories of the event.

We first present a patient who did not remember the car accident, and then a patient who did remember it. Informed consent to publish the details of these two cases was obtained from the patients. This study was approved by the Chonnam National University Hospital Institutional Review Board (CNUH-2021-020). The study was performed in accordance with the Declaration of Helsinki. We used the Clinician-Administered PTSD Scale, Impact Event Scale-Revised (Korean version), Insomnia Severity Index, and Hospital Anxiety and Depression Scale to assess the psychological symptoms and PTSD of the patients [10-12]. The patients’ symptoms are shown in Table 1, pre- and post-intervention.

Patient with No Memory of Their Car Accident

Mrs. A, a 27-year-old female, visited the hospital with psychiatric symptoms, such as negative thoughts, poor concentration, a numbing sensation, and nightmares, occurring after a car accident 2 months ago. She experienced a car crash while riding in a taxi with a friend at night. She lost consciousness at the time of the accident and has no memory of it. Although she did not re-experience symptoms because she could not remember the accident, she complained of PTSD symptoms, such as hyperarousal and numbing, and met the diagnostic criteria for PTSD. She agreed to receive VRET plus medication. We prescribed 50 mg sertraline, which was subsequently increased to 100 mg. VRET was performed for 6 weeks according to the previously described protocol. She consented to experience the accident situation through VR without hesitation. She reported mild dizziness on initial exposure to the VR accident, but not afterward. As shown in Table 1, her symptoms improved after treatment, which was terminated without administering any further medi-cation.

Patient Who Remembered Their Car Accident

A 39-year-old man, B, had a rear-end collision in a tunnel 12 months before the hospital visit. He was fearful at the time of the accident because he thought he might die. Subsequently, he suffered from insomnia, fear of driving at certain speeds, and headache. Even though he was treated with drugs for insomnia and headache at other hospitals, he visited our hospital because the treatments proved insufficient. He expressed anger at the driver of the vehicle behind him, and at the fact that he had to go through such an experience alone. After VRET he remarked that “I have come to realize that accidents can happen to anyone.” His SUD scores at 1 week and after the final exposure are presented in Figure 4. He did not report any side effects or cybersickness. His psychological problems improved after treatment, although his mild headache did not (Table 1). He now has no problems with sleep and has thus stopped taking sleep medications.

As shown in Table 1, our patients showed significant improvement in PTSD symptoms after VRET. ERP therapy achieves fear reduction through habituation, without avoidance, escape, or ritualizing after experiencing the anxiety-producing conditioned stimulus. Foa et al. [4] discussed habituation in terms of emotional processing theory and argued that between-session habituation is the most important element in treatment. According to the habituation model, exposure is effective because it provides structured contact with a feared stimulus while minimizing the opportunity for avoidance, escape, or ritualizing. Thus, habituation through exposure is optimal when fear is activated, avoidance or escape behavior is minimized, and anxiety decreases within and throughout the exposure task [4,13]. Fear activation is thought to be necessary to allow extinction learning to occur in response to a given fear. Exposing a patient to stimuli through VR is optimal for activating fear. As shown in Figure 4, the SUD scores of our patients indicated that the VR traffic accident was appropriate for successful treatment. Unlike image exposure, with VRET the same accident-related stimuli are presented to patients every week, and the therapist can gauge the stimulation provoked by the VR traffic accident. When the stimulus effect is weak, it can easily be increased in intensity. This “dose” effect is important from a therapeutic point of view; through VR, the dose can be quantitatively controlled.

The traffic accident stimuli used herein are shown in Figure 1. However, as each patient’s accident experience is unique, the VR stimuli are not representative of all situations. Furthermore, the optimal level of exposure differs widely among individuals and is influenced by a variety of factors, such as insight, developmental level, and the baseline level of anxiety [14]. The exposure is therefore rarely optimal. Based on our VRET model, we suggest that psychoeducation, cognitive therapy, the stabilization technique, and habituation are all necessary for maximizing the benefits of exposure. Therapists should provide a clear rationale for exposure to a VR accident situation, monitor the patient’s behavior during the exposure task, and help them “work through” the exposure. The stimuli presented to our patients were judged sufficient to provoke the fear necessary for ERP. Our first patient did not remember the accident situation, as stated previously. However, we presented video scenes with consideration of the time and place of her particular accident, to ensure that the stimuli were appropriate for the PTSD treatment.

This report had several strengths. First, we have proposed a process through which to apply VRET. As there is no standardized protocol for VR-related research in this field, our process will facilitate future VR-related paradigms [15]. Second, we recruited patients who were quite motivated to receive the therapy, as it was the first time that they had been exposed to VR.

This report also had some limitations. First, we used a case study design, which is appropriate for understanding the “how” and “why”, but provides results that are not generalizable. In particular, our case study may not thoroughly address the “how” of our intervention. However, the intervention protocol that we developed could guide future treatments. Second, the PTSD severity of our patients was relatively mild, and both of them were young. They had no objections to experiencing VR, and five exposure sessions were completed because there were few side effects. Continuous dialogue with the patients is necessary, where the indications and contraindications for VR exposure therapy have not been established. Future studies on VRET for car accident-related PTSD should utilize a randomized controlled design to account for the numerous potential confounding factors.

No potential conflict of interest relevant to this article was reported.

Ju-Wan Kim and Jae-Min Kim had full access to all of the data in the study and take responsibility for of the data. Study concept and design: Ju-Wan Kim, Jae-Min Kim. Drafting of the manuscript: Ju-Wan Kim, Jae-Min Kim. Critical revision of the manuscript for important intellectual content: Ju-Wan Kim, Sung-Wan Kim, Jae-Min Kim. Administrative, technical, or material support: Min Jhon, Hee-Ju Kang. Study supervision: Sung-Wan Kim, Jae-Min Kim.