Background
Specific phobias are second only to major depression for lifetime prevalence of mental health disorders in the United States (16.6 % vs 15.6 %) [
1]. The prevalence is somewhat reduced in older individuals (8.7 %) [
2]. Estimates suggest 60–80 % of those with specific phobia are hesitant to seek help [
3]. Some phobias are far more common than others [
4], with half of reported phobias being fear of either heights or animals [
5]. Spider phobia is among the most prevalent of animal phobias and is the most studied. The consequences of anxiety, worry, and avoidance behavior can have a large impact on quality of life, work, and leisure activities [
6].
Exposure-based therapies in which an individual is systematically and repeatedly presented with a feared or avoided internal or external cue is highly effective in reducing anxiety disorders [
7,
8]. Compared with imaginal exposure, evidence indicates that an in vivo (naturalistic setting) stimulus is the preferable exposure treatment method for specific phobia [
6]. One-session therapy (OST) is considered the intervention of choice for in vivo specific phobia treatment in adults and children [
9,
10]. OST sessions typically last up to 3 h and consist of graduated exposure to phobic stimuli, positive reinforcement, therapist modeling of non-phobic behavior, and cognitive restructuring of catastrophic beliefs [
11].
The benefits of exposure therapy are limited by issues pertaining to both therapist and patient. Access to evidence-based treatments has been lacking [
12], likely commensurate with the challenges of therapists locating appropriate material and/or stimuli, difficulties with conducting exposure work outside the clinic, and maintaining stimuli such as animals and insects. Even when these resources are available, participants may refuse to engage in therapy. Once explained, exposure therapy is turned down by 30 % of subjects [
13], and this percentage is estimated to be significantly higher for OST if the endpoint is discussed beforehand [
12]. Return of fear of the feared stimuli following treatment can also occur at a later date [
14].
Virtual reality (VR) technology involving head-mounted, motion-tracked displays, accompanied by realistically rendered 3D computer-animated environments [
15], offers researchers the opportunity to recreate phobic stimuli, manipulate and tailor key variables associated with stimulus presentation (color, size, and movement), context, scheduling, and intensity of exposure according to the patient’s needs, as well as to extract unprecedented amounts of data, such as gaze focus [
16]. Previous generations of VR have already been used successfully in mental health treatments [
17] for fear of flying, heights, public speaking, and spider phobia, among others [
18]. VR thus has the potential to greatly increase accessibility and effectiveness of exposure treatments. In a survey of 777 undergraduate students who scored high in fear of spiders, more than 80 % expressed a preference for VR exposure treatment over in vivo treatment [
19]. In recent studies, researchers have evaluated the unique opportunity of VR to inexpensively and relatively easily alter the context of exposure, an important moderator of treatment resurgence [
20]. Participants treated using VR in multiple environments [
21], and participants treated by exposure to spiders using video recordings of multiple areas of a house rather than a single area [
22], were less likely to have return of fear following an aversive event.
Serious games designed for purposes other than entertainment and allowing users to experience situations impossible or dangerous in real life [
23], with gamified elements such as points and goals to increase engagement [
24], may provide a particularly promising advancement in exposure therapy. As reviewed by Botella et al. [
25], game elements may reduce distress as compared with traditional exposure therapy [
26]. Recommendations that patients continue to confront phobic stimuli posttreatment [
12] may be facilitated by gamified VR content that can be played again and again [
25].
The potential of VR notwithstanding, the quality of past VR exposure therapy research has historically been poor [
27]. Well-designed randomized controlled trials are required before implementation in clinical practice can be recommended. Further, recent advances in VR technology have enabled unprecedented realistic stimuli to be rendered with less intrusive equipment, minimizing the risk of nausea and allowing longer sessions, though careful application design is still required [
28]. A new generation of VR systems produced by some of the world’s largest technology companies, such as Sony (Project Morpheus), Microsoft (Hololens), HTC (Vive), and Facebook (Oculus Rift), promises to change VR from a professional niche product costing as much as $35,000 to a consumer product priced around $599 plus the cost of a competent computer [
29]. Other developments in VR include the use of smartphone-based systems such as the Samsung Gear VR, used in the present study, the cost of which is negligible ($99 USD) if paired with a user’s preexisting smartphone [
30]. From a research perspective, using VR can also reduce some of the complexity of carrying out exposure treatments, improve standardization of protocols and cost-effectiveness, and enable at-home self-care [
31].
The parallel-group randomized controlled trial described in this protocol is designed to investigate non-inferiority of a novel, gamified VR OST program for spider phobia by comparison with traditional OST.
Discussion
The aim of this study is to evaluate the effectiveness of VR exposure therapy compared with traditional one-session exposure therapy using a randomized controlled design and subjects diagnosed with spider phobia. The introduction of modern VR headsets combined with powerful but relatively inexpensive computers capable of displaying realistic stimuli, in addition to the historical lack of high-quality randomized controlled trials [
52], suggest that this is an opportune time to make use of this rapidly advancing technology and translate it into clinically validated mental health treatments. VR exposure therapy has already been theoretically and empirically evaluated to be well-suited for the treatment of specific phobias [
53]. The authors of a recent meta-analysis [
54] provided additional evidence based on behavioral assessment rather than self-report of internal states. VR exposure-treated subjects, in their review of 14 studies, improved significantly after treatment (
g = 1.23) and compared with control subjects (
g = 1.41). No significant differences were identified after treatment and in follow-up between in vivo and VR exposures.
Conducting VR exposure therapy using modern, commercially available VR equipment may prove even more powerful. In addition to the evaluation of modern VR hardware, our intent in this study is also to evaluate a newly developed, gamified exposure application for the treatment of specific phobias. The software includes advancements such as multiple open-ended exposure scenarios relying on gamification to improve engagement and interest; multiple stimulus intensity variables such as appearance (small to large spiders, cartoon-like to hairy), behavior (more or less predictable, static, and aggressive), a variable number of spiders, and changes in lighting and protective barriers (such as caged or not); a virtual therapist that guides the participant in the use of the application and provides psychoeducation and expert advice about spiders; and inclusion of a gaze direction trackpad to allow participants to interact with the stimuli.
Recent evidence indicates that treatment benefits of exposure therapy accrue as a result of new inhibitory learning and not habituation of the conditioned response to phobic stimuli [
55]. Physiological habituation (viz., reduced heart rate and galvanic skin response) may serve as a safety signal alleviating fear in the short term but inhibiting long-term learning and extinction [
56]. Serious game treatments in which there is a sense of play, interactivity, flow, and creative solutions have the potential to promote new learning [
57]. In an exposure therapy context, these should create engagement (rather than avoidance) by producing a mismatch between expectancy and outcome and require flexible responding [
55]. In a study in which a fear of heights group received random levels of exposure intensity and approached stimuli in multiple ways versus a steady intensity increase group, researchers found improved fear reduction in the former, without a need for physiological habituation [
58].
Limitations of the present study include an exposure application that involves multiple unique design specifications, making disentangling of specific therapeutic factors difficult. Despite the complete automation of the VR application, psychologists will be in attendance to resolve technical difficulties and ensure treatment compliance and will be present to assist patients if needed. Future studies will benefit from having the patient administer VR treatment independently to ensure true isolation of treatment effects. In addition, physiological monitoring of subjects will not be possible during this study but may prove helpful in interpreting the results of future studies.
In sum, spider phobia is a common disorder [
1] that has a negative impact on life, work, and leisure activities [
6] but goes largely untreated [
3]. VR exposure therapy may provide improvements in efficacy [
15], access, standardization of protocols, and cost-effectiveness [
31]. Although not evaluated in this study, virtual OST also has the potential to conveniently continue maintenance therapy once regular treatment has been completed. This study is, to our knowledge, the first to test the efficacy of a modern, market-ready VR application for the treatment of spider phobia, and it will assist in the development of a new method for the delivery of evidence-based treatments.
Acknowledgments
The present study was made possible in part by a grant from the Swedish Research Council (2011-2913) and Forte (2013-1107). The authors extend their gratitude to Katherine Cotter for assistance in executing the trial, and the following clinical psychologists: Daniel Attar, Stefan Deak, Maria Garke, Julia Heinsoo, Sofia Jägholm, Glenn Kristoffersson, Jonas Rafi, Kerstin Sindemark, Jessica Sjölund, Linnéa Törnhage, and Maria Zenger.
Competing interests
WH is the founder of Mimerse, the private company that developed the VR application used in the present study and which is intended for release on the open market. Hence, WH will not be involved in data analysis or any decisions related to the publication of findings. The other authors declare that they have no competing interests.
Authors’ contributions
AM drafted the manuscript. All coauthors made contributions to sections of the manuscript and provided critical review. PL, AM, PC, and LR designed the study. WH, GA, and PC made significant contributions to the conception of the study. LR provided clinical OST training and supervision. WH created the VR application. All authors read and approved the final manuscript.