key: cord-0303161-ud7qadx9
authors: Olatunji, Omisore; Odenigbo, Ifeanyi; Orji, Joseph; Beltran, Amelia; Orji, Rita; Baghaei, Nilufar; Sandra, Meier
title: Extended Reality for Anxiety and Depression Therapy amidst Mental Disorders -- A Systematic Review
date: 2022-04-04
journal: nan
DOI: 10.2196/preprints.38413
sha: 16c5a4aa492015c9618d86c6c03ae61ca251c980
doc_id: 303161
cord_uid: ud7qadx9

This systematic study is aimed to investigate the implementation level of different extended reality (XR) techniques in the care of mental disorder. We point out some XR technologies used to deliver care for mental disorders, and to evaluate the effectiveness of using XR systems for anxiety and depression amidst other mental disorders. A search period of May 2017 and August 2021 was defined to filter out articles related to the usage of virtual reality (VR), augmented reality (AR) and mixed reality (AR) in a mental health context. Search done on three databases namely Google Scholar, PubMED, and Association for Computing Machinery Digital Library yielded 689 articles. Also, 10 articles were recommended. Upon eligibility filtering, only 72 articles were found relevant and were utilized for the study. Results show that the 72 studies were done in only 23 countries across the globe, with the majority of studies being reported for developed countries such as USA (20.64%) and Germany (11.11%). Thus this could rapidly aid intervention of mental health disorder with XR. Meanwhile, none of the studies observed was from an African country. The majority of the articles reported that XR techniques led to significant reduction in symptoms of anxiety or depression. The majority of studies (23, 36.51%) were published in the year 2021 of the total studies included. In a sense, this data might be attributed to COVID-19 pandemic. Most studies (30, 47.62%) focused a population with age range of 18 to 65 years, while fewer studies (4, 6.35%) focused on each of adolescents (10 - 19 years) and seniors (over 64 years). Also, more studies were done experimentally (52, 82.54%) rather than by analytical and modeling approach (5, 7.94%) as found in other XR studies domain. This review study could aid the development of XR systems for effective cognitive behavioral and exposure therapies of mental disorders.

Mental disorders are defined as behavioral or mental patterns that cause significant distress or impairment for an individual. Mental disorders are highly prevalent and configure a leading cause of disability. Over the last decades an global increase in the incidence rates of these disorders has been observed, which got further aggravated as a result of the recent COVID-19 pandemic [1, 2] . Currently, mental services are limited in their accessibility intensifying the societal struggle to meet the demands of more and more patients in need across the world. According to the World Health Organization (WHO), mental disorders are the leading cause of disability in United States and United Kingdom with almost 20% of adults experiencing mental health problems annually [3] . In addition to adult group, adolescents patients are characterized with highest incidence of mental disorders in Canada and this group have very least reporting rates in the country [4] . According to a recent epidemiological survey shows that acceleration of socioeconomic developments increases the prevalence of mental disorders (17.5% amongst adults) in China [5] . WHO predicted the untreated mental disorder to account for 13% of the total burden of diseases by 2030 [6] . While over 75% of people with mental disorders remain untreated in developing countries, 35 -50% of the corresponding range is also found in high-income countries [7] .

Amongst all, anxiety and depression remains the most common mental disorders in the society [8] . The reported cases characterized 1 of 13 of the mental disorders as anxiety with major depressive and specific phobia disorders [9] . WHO estimated that these conditions cost the global economy roughly $1 trillion in lost productivity costs annually [10] . Anxiety or mood disorders are closely linked and individuals who develop depression have often experienced an anxiety disorder at some earlier point(s) of life [11] . While the etiology of anxiety disorders and depression is complex, multiple causal factors such as rapid social change, stressful work conditions, gender discrimination, social exclusion, unhealthy lifestyle, physical ill-health, human rights violations, as well as genetics have been appropriately studied. Reports mostly suggested that closer mental care should be addressed by increasing accessibility and the development of tools that patients can use on their own.

Mental health therapy majorly involves joining social, cognitive and behavioral factors into treatment procedures [12] . Cognitive behavioral therapy (CBT) is a conventional treatment approach that has been used and shown to be effective for a range of mental disorders such as anxiety disorders, depression, phobia, alcohol and drug use problems, and severe mental illness. CBT dwells on aiding patients follow up as their own therapists; thus, it is widely used to treat anxiety disorder and depression. Psychotherapy and psychosomatics are two forms of CBT used in treating anxiety disorder. [13] . It became popular as a first line treatment since 1980s, and mostly involves talking out matters that surrounds the anxiety disorder with patients. It works better than (with) medication commonly in anxiety treatment, and well supported by many guidelines [14] . Studies have also shown that CBT is an evidence-based therapy that reliably helps in overcoming depression. However, CBT and medication are combined as a first line treatment option for depression [15] . CBT procedures involve aiding people to identify and change bad lifestyles that negatively influences their behavior and emotions [16] . Indeed, rather than been a set method, CBT is a combination of techniques based on a disorder being treated. For instance, the treatment procedure for depression is different from how CBT is used in treating phobic and other anxiety disorders.

Exposure therapy is a major element of CBT-based treatments for anxiety and related disorders. In this approach, subjects are exposed to feared objects, activities or situations in a safe environment, and this is known to reduce patients' fear and possibility of avoidance. With gradual follow-up, such subjects can be helped to overcome their anxiety [17] . The variations of exposure therapy can be majorly classified based with respect to their application context as conventional (including in-vivo and imaginal exposure) and modern exposure. During in-vivo exposure, patients are intentionally faced with real-world objects or situations they feared to reduce their anxiety [18] . However, this exposure therapy method only works for a small percentage of patients despite. Imaginal exposure configures an alternative approach during which patients confront their fears in their own mind by imaging worst outcome scenarios. The effectiveness of this approach depends on patients' motivation and ability to generate these fear-inducing imaginations. Exposure therapy is challenging as therapists require extensive training and multiple long exposure sessions. Thus, the conventional therapy method is time-consuming and costly. Recently, XR have been evaluated as new delivery form for exposure-based therapy of mental disorders. Their potentials for anxiety and depression have been well reported.

Extended reality (XR) an umbrella term referring to all real-and-virtual combined environments and interactions generated by computer technology has been recently conceived for managing mental health disorder such as anxiety and depression. This recent technology is rapidly gaining traction in creating imagination of real worlds through virtual, augmented, and mixed realities. Thus, patients of certain mental health disorders can be virtually immersed to allow them display and confront health disorders they suffer from. XR technology is playing more of a prominent role in different sectors such as providing clear benefits in many aspects of work and business, including training, collaborative working and marketing. It has been noted that the development of XR can transform the health domain remarkably; however, an exciting issue is studying its impact on the future of mental health [19] [20] [21] . On the industry sector, recent reports shows that XR medical market is estimated to reach USD 1.7 billion in 2022, with a compound annual growth rate of 105.6% from 2018 to 2022. Thus, proving XR solutions will play a crucial role in the future of medicine. As the market continues to grow, it safe to assume that development of XR technologies for treating mental illness will significantly increase over the next decades.

XR involves one or more of VR, AR and MR technologies to create exposures. Virtual reality (VR), augmented reality (AR) and mixed reality (MR) involves using computer models to artificially design real world environments with visual or other sensory features, and simulating typical contexts that induce anxiety, phobia, or pain to enable users interact with the environment. Development of the artificial environment typically consist of four main components 1) a high-end graphics rendering unit that is used to compute and render virtual scenes through a frame buffer; 2) 3D stereo display unit that connects users' visual sensory to the environment; 3) a tracking system that models users' movement in the virtual environment; and lastly, 4) other input interfaces such as joysticks or sensory gloves which provide tactile feedback. Results from increasing number of studies suggest that that this form of therapy is effective as the conventional exposure-based methods. [14, [22] [23] [24] . It is anticipated that XR technology might the greatest promise for mental care [14] . XR-based exposure therapies are accessible and offer lasting improvements for anxiety and depression. Following the numerous therapy designs that have been studied, many robust systems with various platforms and formats are available to provide care for different mental disorders [14, 22, 25, 26] . XR systems have been successfully applied in individual, group-based, and internet-based settings [27] [28] [29] . It started more than two decades when Hoffman's team [30] developed a VR gaming system for exposure-based therapy in mental care. The SnowWorld provides a system of reducing players' pain perception during burn wound care. Anderson et al. 2017 presented a follow-up of the first randomized clinical trial to test another format for delivering cognitive behavior therapy for social anxiety disorder-virtual reality exposure therapy. The study showed virtual reality and exposure group therapy has been well established as an effective treatment for social anxiety disorder. We hypothesized that this is well used for managing anxiety and depression therapy amidst many types of mental disorders.

Delivering mental health treatment with extended reality has shown three potential transformations to current mental health care. VR or AR environments provide greater degree of control for therapists to customize, reproduce and tweak several treatment parameters according to an individual patient's needs. Such parameters include fan wind, stereo sound, moving chair, color display, and odor emitters [31] . This kind of customization may not be achieved in traditional exposure therapy [32, 33] . Also, risks of privacy intrusion are reduced as everything is confined to a virtual environment [34] . Furthermore, the simulated and augmented environments are less scary than the conventional exposure therapy according to the patients [30] . Exposure-based therapies defined on VR/AR/MR applications show to be effective in the treatment of a variety of other mental health conditions. This study presents findings from a systematic review on the state-of-the-art XR-based exposure therapies for supporting anxiety and depression.

This systematic review is carried out to investigate the implementation level of XR -VR, AR, and MRin the clinical care of depression and anxiety. The review was conducted in with the guidelines outlined Arksey and O'Malley [22] . The main objective of this systematic review is to show the implementation and usage levels of XR-based therapy in providing care for anxiety and depression amidst other mental disorders. The technology-based health intervention domain is advancing rapidly recently; thus, it critical to analyze the current state-of-the-art XR techniques that have been lately developed and used to provide care. Thus, we set the review study on a) the technological design and usage of XR in providing care for mental disorders and demographic focus on anxiety and depressive disorders; b) the components that characterize XR system setups in mental disorder contexts; and c) the effectiveness of XR technology for anxiety and depression as top mental disorders.

We formulated a search strategy that was used to explore multiple databases and find all recent and relevant research articles about XR technologies to support the evaluation and treatment of depression and anxiety disorders amidst other mental health disorders. The systematic searches were conducted primarily on PubMED (https://pubmed.ncbi.nlm.nih.gov/advanced/), Google Scholar (https://scholar.google.com) and Association for Computing Machinery (ACM) Digital Library (https://dl.acm.org/search/advanced) databases. The search period was defined to filter out all articles that were published between August 2016 and August 2021 and indexed in any of the three databases. The three databases were chosen as they provide simple and quick ways to search across a variety of disciplines, databases, and journals, and as well have the most complete indexes of articles that focus on the theme of this review study. Multi-level filtering was carried out following the PRISMA guidelines to limit the search outcomes to relevant studies providing the most valuable data to answer our research questions. The search strategy was set to limit the our data sources to studies that implemented or used one or more of VR, AR, and MR for exposure-based evaluation or therapy of depression and anxiety disorders amidst other mental disorders.

The search terms were discussed amongst the research team and were defined as "Augmented Reality", "Mixed Reality", "Virtual Reality", "Depression", and "Anxiety", "Mental Health". These search terms are the most appropriated keywords that are reflected in the studies that have utmost relevance to our research questions. The full terms were exclusively used during the search to avoid any potential conflicts with other terms such as VR intended for "Virtual Reality" extracting use of related acronyms (e.g., Voice Recognition) which would make the filtering cumbersome and not necessarily generate additional useful resources. The selection criteria were carefully designed to consider articles that contain one or multiple search terms in the title and/or abstract sections of the papers, while further steps explained below are followed to ensure that the article focuses our prospect. In addition, only articles published in peer reviewed journals and conferences (with oral presentation) were considered. Advance search sections of the three databases allow extracting more relevant articles only by using a set of limiting criteria. For instance, when we used the search filter criteria "anywhere in the article" with the defined search terms, 536, 109, and 34 search results were scrapped from PubMED, Google Scholar, and ACM Digital Library databases, respectively. Additional 10 records were also identified through professional source. Based on our search strategy and study goal, we decided to use a combination of two search rules namely; i) all the search terms must be present in the article' title and/or abstract, and ii) the article publication year must be within a specific range between August 2016 and August 2021. Additionally, exclusion criteria were defined that all i) duplicate articles, ii) version updates, iii) articles written in language other than English, iv) studies that reported anxiety or depression as a secondary aspect or induced illness, and v) articles presenting SWOT analysis, thesis and citations, and systematic reviews were filtered out.

The search strategy yielded 679 articles scrapped from the data sources, and the supplementary 10 articles identified through professional source. The articles are processed as shown in Figure 1 . First, irrelevant and duplicate articles (i.e. 226 articles) were removal; thus, a total number of articles to 453 were left. Next, the remaining articles were for further screened for relevance. This started with title screening and the results obtained were reviewed for bias and attrition removal. A total of 172 texts were removed in this step. Full abstract reviews were done in situations when an article's relevance could not be resolved with title. Thus, 100 articles were further screened out. Yet, authors carried out full-text review when certainty on an article's relevancies was still lacking to make up the assessment. In total, 272 non-relevant articles were screened out by the authors leaving only 181 articles sought for retrieval. A second screening step was required to limit the systematic review to articles that fulfill the eligibility criteria. Thus, further assessment was carried out and another 108 articles were removed. Full-texts of 73 articles were retrieved. Articles out of context (n = 8) and those lacking quantitative data (n = 2) were also excluded. Finally, a total of 72 articles that meet the eligibility criteria were included in this review study.

Three of the authors performed the data extraction process while the data validity and accuracy were checked by a fourth author. The full texts of the 72 articles were downloaded and shared amongst the authors for review. Specific details of the articles listed below were extracted and processed in a spreadsheet to analyze the adoption of VR, AR, and MR in managing anxiety and depression and related mental health disorders.

1. Publication authors, year, and regions; 2. The study type and study design focus and health domain; 3. Methodology e.g., study duration, number of sessions, and duration in minutes; 4. the study methodology was based on and evaluation strategy; 5. The VR/AR/MR application and technology (type of headset, toolkit) used for the study; 6. Study demographics such as targeted population, sample size, and age distribution; 7. The motivational strategies, targeted outcome, and region; 8. Key findings on the using the XR techniques for managing depression and anxiety.

The details related to the abovementioned data were utilized to address the two specific questions raised in this systematic study. Basically, the data provided useful insights on developing statistics of the data sources referred in this systematic review. For instance, we could aid understanding of developers and researchers on how to aptly set VR/AR/MR system with the extracted data. Similarly, users can learn about significance of such systems when approaching XR-based exposure therapy for their mental health.

This systematic review was based on a total of 72 articles [25, 26, 32, (see Appendix 1) selected by following the steps discussed in Figure 1 . First, we analyzed the country of origin of the articles. The 72 studies have been conducted by 25 countries across the globe, as shown in Figure 2 . 19.44% (n = 14) of the studies were carried out in the United States, and this is followed by Germany (n = 8, 11.11%). Compared with the previous study [16] , it may be said that both countries dedicated a good amount of research fund and time to study how XR aid mental health care in the countries. Moreover, our data shows that a good number of studies have been reported from the Netherlands (n = 6, 8.33%) and South Korea (n = 5, 6.49%). These countries have good development and economy attraction from XR related electronics. Our study infers that, compared to the remaining 21 countries, the Netherlands and South Korea countries dedicated the domestic technological development for XR-based mental disorder studies. Meanwhile, none of the studies was reported from an African country. This either shows a weakness in providing mental health services in the continent or blind eye turned to mental disorder in Africa [105] .

In terms of study frequency by year, Figure 3 shows that the majority of the articles 38.89% (n = 28) were published in the year 2021, i.e. of the total studies included. Thus, this further underlines the priority to advance mental health care. In a sense, this data might be attributed to COVID-19 pandemic. Global prevalence of anxiety and depression increased by 25% in the first year of the pandemic, while the psychosocial effects of the pandemic varies with regions [106, 107] . Also, Figure 3 shows 

We analyzed the age of participants included in the studies as shown in Figure 4 . Depending on the inclusion age groups specified by the primary authors, we categorized the study participants as Children, Teenagers, Adolescents, Young Adults, Young & Old Adults, and Old Adults based on the age ranges reported in those 72 studies. We declared studies that omitted such information as "Not Specified". For this, we analyzed the maturity levels of the participants found in most studies. A substantial age overlap was found amongst the groups of individual included in the reviewed studies. Thus, we classified as Adults where participants ages were specified to be between 19 and 65 years in the reported studies, and as Older Adults where the participants that aged above 65, inclusive. As plotted in Figure 4 , we observed that more studies (n = 35, 48.61%) were designed for adults. It is found that small number of studies focused on younger subjects. For this age group, nine of the 72 studies (n = 9, 12.50%) focused on participants between the age of 0 and 12 years, and only 4 of the 72 studies (5.56%) focused teenagers' group as well. Having such number in these groups could be due to lack of standard way for selecting audience when developing XR systems for managing mental disorders [108] . Furthermore, to reflect the level of age diversities in the studies, we analyzed the mean age distribution of the participants that were included in each article. Aside the statistical information derived from the age groups (in the bar chat of Figure 4 ), the mean age distributions of the participants were pinned as pie chart in Figure 4 . The data indicates that majority of the studies (n = 43, 59.72%) were designed for audience with a mean age of 35.079 ± 9.72 years. The age distribution in this group is particularly dominated with lower and upper values of 18 years (n = 16/43) and 65 years (n = 5/43), respectively in the different participants' age ranges. The youngest participants that admitted use of XR for mental disorder study are a group 4 -8 year children that were investigated to see how VR reduce anxiety perception in infants [73] . 

Furthermore, we analyzed the sample size of participants admitted and found eligible in the 72 studies. We partitioned the sample size into five different categories and analyzed the number of studies as shown in Figure 5 . The plot shows that participants between 21 -50 people were recruited in 29.17% of the studies (n = 21), closely followed by having 51 -100 people in 22.22% (n = 16) of all 72 studies. Furthermore, 16.67% (n = 12) studies included over 100 participants while very small sample size (≤20 participants) were considered in 27.78% (n = 19) of the 72 studies. Most of the studies in latter were more subtle in their findings and conclusions. Thus, it can be understood that having relatively more participants is helpful to reach cognate conclusions. Overall, all the study categories were reported in at least 10 studies except in the case of using 11 -20 people which was found in only 9 studies (12.50%) and another three studies which did not specify their subject's population. The participants' gender distributions were not analyzed as this data was missing and could not be deduced is a significant number of the articles included in this systematic study. 

Application of XR systems for mental disorders requires vigorous study and implementation strategies.

The design of the studies included in this review varied substantially. With a focus on anxiety and depression, the four main types of studies that were are carried out are i) "discussion" which are studies with a narrative focus; ii) "experimental": studies that were done to investigate the effect of the XR techniques on certain groups of subjects or other factors that aid or affect such setup; iii) "modeling" which includes studies that were done to develop new model or setup and such were validated on limited subjects or data; and lastly, iv) "analysis" which are the studies done without any particular experimental study but relying on data of previous experimental studies. As shown in Figure 6 , it was found the 80.56 % (n = 58) were designed with experimental studies and reported how XR could aid intervention of mental health disorder out of the four categories. Meanwhile, the studies in the modeling and analysis categories only consist of 8.33% (n = 6) and 9.72% (n = 7) of included studies respectively. Studies with pure narrative are very few as the Discussion studies account for 1.39% of the 72 studies. This review shows most studies were done under experimental investigation. Typically, this enables direct comparison between the mental conditions and relationships with their causal factors in psychological cornerstone studies [109] . Furthermore, 54.17% (n = 39) of the included studies were focused on investigating the effects of XR immersion level used in the studies. This shows that researchers in this domain are commonly fond of investigating how immersion can influence the mental health procedures. The other design factors of the XR systems found in the 72 studies are on subject's personalization (n = 12, 16.67%), and cases of manual system designs which were typically focused in 4 studies (5.56%) and automation (n = 7, 11.11%) process. The latter were majorly investigated to observe if real-world situations and environment are well emulated in the studies.

In addition, we analyzed the common evaluation categories reported in the 72 studies. First, categories of study periods (in weeks) and the duration per session (minutes) were analyzed with respect to the number of sessions in the studies. As presented in Figure 7a , most of the studies were carried out in 1 -5 weeks (n =22, 30.56%) and 1-5 sessions (n =30, 41.67%), respectively. Other studies followed their participants up to 6 -10 weeks (as found in 8 studies 11.11%,) and 6 -10 sessions (as found in 13 studies 18.06%), and even 11 -15 weeks or sessions as found in 5 studies (6.94%) or in 6 studies (9.52%), respectively. It is noteworthy to emphasize a few studies (n = 1, 1.39%) lasted 16 -20 (weeks or sessions) while n = 2 (2.87%) and n = 3 (4.17%) were conducted for in 21 -50 weeks and sessions, respectively. Lastly, one study was reported to have been carried out in over 90 sessions [110] . This was a pilot-study developed with structured model for restoration of socio-cognitive in children (aged 8-13 years) with acquired brain injury. A total of 32 children participated. Each session typically required longer exposure duration. Furthermore, we analyzed the duration per session (in minutes) for the sessions that were reported in each of the studies. In most of the studies (n = 42, 58.33%) participants used XR techniques for 0 -30 minutes. This is followed with studies requiring with 31 -60 minutes (n = 12, 16.67%) and 61 -90 minutes (n = 3, 4.17%) of user engagement per session. On the extreme end, in one study XR techniques were used for a session with duration of 120 minutes and even up to 180 minutes in another study. It was observed that n = 10 studies (13.89%) did not specify the duration spent per session. In addition, we analyzed another common evaluation category used in most of the studies included in this review. Three main methods were identified and these are quantitative, qualitative, and mixed evaluation methods. Overall, quantitative assessment approach is applied in 52.78% (n = 38) of the 72 studies and it is understood that qualitative method reveals deeper insights about the XR-based interventions. Furthermore, quantitative method was used in 11 studies (15.28%), while mixed method was found in 21 studies (29.17%). We also found that the evaluation methods were not reported in 2 studies see Figure 7c .

Analysis of the XR techniques that are currently being utilised in the care of depression and anxiety is important. We first analysed the major strategy found in the studies included in this review. During review the XR interventions in each study are decided as gamified or otherwise. As shown in Figure 8a , 34.72% of the studies (n = 25) adopted gamification strategies and this strategy has been used across 18 mental health conditions in the 72 articles. The few exceptions where gamification strategy was not applied are pain and anxiety, negative thoughts, autoimmune disorder, and acquired brain injury. Conversely, non-gamified strategy was adopted in these conditions as well as in all other mental health conditions found in the included studies. It can be concluded that the gamification strategy are yet to be found used for some certain conditions such as the autoimmune disorder and acquired brain injury. A possible scenario is maybe such technology is not suitable of research studies are on-going to show its applicability. In addition, we analyzed the XR applications that have been used in the study and found specific systems such as 3D Unity to be commonly reflected by many authors. Only 49 studies of the 72 articles (66.67%) reported the XR applications used in the studies. Many of the applications were only found in one study and these accounts for 49% of the studies (listed in Appendix). As shown in Figure 8b , the exceptions to these are the Unity Pro which was used in 13 studies (26.53%), as well as the Blender and Mobile virtual systems were used in 2 studies each (4.08%).

The most frequently used XR application is the 3D Unity Pro and that is probably due to its powerful editor to create XR assets, and its cross-platform development support. Similar, we observed that a number of studies (n = 8, 16.33%) have been carried out with custom VR systems. Such adaptive applications are either newly developed or adopted in those studies and evaluated for providing care to mental disorders.

Although this systematic review is focused on anxiety and depression, mental health disorders have very ambiguous borderline definitions; thus, we reviewed the 18 cases of individual mental disorders in the 72 articles, and illustrated count of the clinical conditions per publication as shown in Figure 9 . Overall, it was observed that most of the XR studies centered around on anxiety and depression (n = 35, 48.61%). These include use of XR for anxiety without depression in 82.85% (n = 29) of the studies, while a minimal attention (n = 3, 8.57%) was focused on depression without anxiety. Typically, 20.27% (n = 15) of the studies focused on just anxiety, while the remaining 14 studies combined anxiety either in general terms or together with other mental disorders. Also, we found another 9.72% of the studies (n = 7) focused on social anxiety disorder. This condition was combined with unclassified distress in some studies [79, 111] . Additional 11 studies (14.86%) were found to have applied XR technologies for phobia (fear disorders that is a clinical diagnosis of anxiety). Use of XR for other mental disorders without anxiety or depression was also studied. For instance, Alzheimer's Diseases like dementia was investigated in 5 studies (6.94%). Comparably, mild cognitive impairment, posttraumatic stress disorder, and autism spectrum disorder were also investigated in similar strength. We found that both were investigated in 5.56% of the studies (n = 4) each, and these are followed by public speaking anxiety reported in 3 studies (4.17%) studies. Unlike in Baghaei et al [112] , we see that generalized anxiety disorder was investigated as specific clinical conditions in 2.78% (n = 2) studies. Beyond this, the other mental disorders were either found in only two studies (i.e. 2.78% each as the case of alcoholic use disorder, psychological stress, and attention disorder) or only one study. The latter are cases of negative thoughts, autoimune disorder, and acquired brain injury (n = 1, 1.39% each). These show that adoption of XR is mostly adopted for diagnosis and treatment of anxiety disorder amidst all mental disorder conditions. This includes studies that solely focused on anxiety and those where depression is studies with anxiety or isolation.

Finally, this systematic study shows that XR-based interventions are distinctly applied for anxiety and other mental disorder that excludes depression. A typical case includes development of XR system for anxiety and phobia as well as anxiety and psychiatric disorders [103, 113] (b) Development Environments positive of XR for evaluation and treatment of mental disorder was identified in the articles that were reviewed. Recent studies show that VR yields similar effectiveness as exposure-based therapy in reducing anxiety symptoms [114] . It is found that Alzheimer's diseases, attention and hyperactivity disorders, and autism spectrum disorders are the common neurodevelopmental disorders treated with the XR-based technology. This section also clarifies the use of VR technology in anxiety; however, it shows that AR and MR have been recently emphasized as add-on technology and not as substitute. It becomes clear that more studies are still needed for evaluating how AR and MR can singly improve mental health.

To further fulfil the aim of this study, we extracted information of the technologies used to deliver the mental health care in the 72 studies. For inclusiveness sake, we only reckoned with the hardware components that were listed to have been used in setting up XR environments in those studies. As it can be seen from Figure 10a , headsets was consistent in 53.85% (n = 35) of the 65 studies that listed the hardware used. This is the most commonly used component when setting up XR for care delivery in the context of mental disorders. Another commonly found components that are smartphones and 3D VR glasses which were found in 10.77% (n = 7) and 7.69% (n = 5) of the 65 studies. We refer that the typical component are becoming increasingly popular in this study domain, and are majorly found in studies that adopted the gamification strategy.

We further analyzed the most popular headset types and found this including headphones, earbuds, and VR head mounts. The latter is a more advanced technology and a basic component in most XR studies. As it can be seen from Figure 10b , nine (9) different types of head mounts were listed in 30 of the 35 articles; Samsung Gear VR was the most utilized head mounts in setting up XR environment and that is found in 8 studies (26.67%). This is followed by the 3D VR glasses which was used in 6 studies (20.00%), and the HTC Vive which was also used in n = 5 (16.67%) studies. In addition, the Oculus Go and Google VR Box which were used in 3 studies (10.00%) each. Two articles reported to have used Oculus Rift in their studies, while different types of VR simulators such as the Oculus CV1, a custom EEG cap with VR head display, and Windows MR headset were used in 1 study (3.33%) each. 

Gamified Non-Gamified 

Following the review of the literature included in this systematic study, it can be concluded that XR systems are commonly used for anxiety and depression amidst other mental disorders. The technologies was used for anxiety and depression in 48.61% (n = 35) of the 72 studies included in this systematic review. The majority of the studies were majorly targeted at cognitive and behavioral change (n = 27, 84.90%) that is subjects going through care are expected to improve in their behavior and/or attitude. This is found in line with conceptualization of persuasive computing. The studies reported that the XR systems help reduce the symptoms of anxiety. Thus, it can be concluded that the virtual environment are effective as exposure therapy in treating mental disorders. We found studies investigating if gamified XR is also effective for reducing acrophobia. The stimuli presented using AR could indeed induce physiological alteratons in the participants [47, 115] . Bras at al. [47] shows that AR and VR offer high levels of immersion and are optimal solutions for counteracting the effects of in-vivo exposure. Joanneke et al [90] showed that, by engagement and cognitive biofeedback, gamified VR can reduce anxiety symptoms. In another study, Veling et al. [103] showed that VR relaxation has positive affective states and short-term effects on perceived reducing psychiatric stress and anxiety symptoms disorder compared to standard relaxation exercises.

Furthermore, it was observed that XR technologies have been applied for providing care to depression either discretely or when found with other mental disorders. A total of 6 studies (17.14% of the 35 studies) considered depression therapy through XR. Three studies [26, 98, 116] show that VR has good efficacy when used for treating anxiety and depressive symptoms in patients with the mental disorders. Similarly, Li & Luo [62] established that gamified XR can reduce depressive disorders through cognitive empathy and mutual understanding amongst patients and caregivers. In comparison to the reference standard CBT, Montesano et al. [72, 117] improved the psychotherapy of depressive disorder in young adults by developing effective VR-enhanced personal construct therapy. These show that recent development of XR technologies are gaining treatment traction for anxiety.

The following limitations should be considered when interpreting the results of this review. The developed search strategy was limited to using PubMED, Google Scholar and ACM databases for efficient and accurate search results. This may have excluded qualified articles from additional databases. (a) Technologies in used XR studies 

We also found that the number of weeks for 33 studies (52.38%) and number of sessions for 18 studies (28.57%) were not specified in the articles included in this review. The former has a significantly larger percentage in the number of studies considered in this systematic review. Thus, it is hard to assert the best number of weeks and number of sessions needed for validating use of XR-based technology in mental disorder treatment. This study has identified different major methodological approaches and development points that have been studied in the recent time. Another limitation of the study is the lack of scientific assessment of the quality of the publications that were included in the systematic review. Moreover, due to the large number of articles reviewed, there is a possibility of overlooking valid publications that might have met the inclusion criteria. Non-English articles were not included in this review either.

Extended reality therapy has been used widely for treating a variety of mental health conditions. This study is designed as a systematic approach of investigating the adoption of XR in mental health disorder: a systematic review on anxiety and depression. The review covered 72 studies which used different types of VR, AR, and MR technology for managing various syndromes of mental health disorder around anxiety and depression. The study observed that, majority of the articles reported in this domain demonstrated a reduction in symptoms of anxiety or depression with the use of XR. Moreover, the studies adopted unique designs that are set up to record the effects of the mental health and formulating appropriate therapy for improvements. We also found that XR techniques have offered very effective approaches with high level of users' acceptability in a range of 18 mental health conditions. Although a considerable number of studies (n = 72) were included in this systematic review, some areas are still under research thereby lowering the percentage of such studies to be included. For instance, adoption of non-gamified strategies is found to have cut across 18 mental health conditions included in this review study. However, studies with gamification strategies were not found on investigating pain and anxiety, negative thoughts, autoimmune disorder, and acquired brain injury. With respect to the second research question, we found that many studies were designed to focus only on anxiety (n = 14, 22.22% of studies) unlike a limited number studies found to have solely focused on depression (n = 2). In a previous study, Baghaei et al [112] also shows that supporting people with depression in XR settings is an interesting area to explore for mental health care. As presented in Appendix 1, only 17.46 % (n = 11) of the included studies carried out randomized controlled trials to study the usage of the XR techniques. Thus, future works are recommended to conduct RCTs for investigating the use of XR technologies and scenarios outlined in testing the effectiveness, benefits and costs of XR in the mental disorder management.

The impact of stress on body function: A review

Health, Psychosocial, and Social Issues Emanating From the COVID-19 Pandemic Based on Social Media Comments: Text Mining and Thematic Analysis Approach

Global Burden Of Disease Studies: Implications For Mental And Substance Use Disorders

Prevention and early intervention in youth mental health: is it time for a multidisciplinary and trans-diagnostic model for care?

Development and challenges of mental health in China

Global burden of mental disorders and the need for a comprehensive, coordinated response from health and social sectors at the country level

Global burden of mental disorders and the need for a comprehensive, coordinated response from health and social sectors at the country level EB130/9

Integrated mental health services in China: challenges and planning for the future

Epidemiology of anxiety disorders in the 21st century

Investing in treatment for depression and anxiety leads to fourfold return

Increased mortality among people with anxiety disorders: total population study, The British journal of psychiatry : the journal of mental science

Family Interventions: Basic Principles and Techniques, Indian journal of psychiatry

Cognitive-behavioral therapy for anxiety disorders: an update on the empirical evidence

Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for the treatment of panic disorder, social anxiety disorder and generalised anxiety disorder

Cognitive Behavioral Therapy for Depression, Indian journal of psychiatry

Designing Individualised Virtual Reality Applications for Supporting Depression: A Feasibility Study

Exposure therapy for posttraumatic stress disorder, The Journal of Behavior Analysis of Offender and Victim Treatment and Prevention

A controlled study of virtual reality exposure therapy for the fear of flying

Is Virtually Everything Possible? The Relevance of Ethics and Human Rights for Introducing Extended Reality in Forensic Psychiatry

Extended Reality in Medical Practice

Toward a user-centric classification scheme for extended reality paradigms

Virtual Reality and Exposure Group Therapy for Social Anxiety Disorder: Results from a 4-6 Year Follow-Up

The Effect of Augmented Reality and Virtual Reality on Inducing Anxiety for Exposure Therapy: A Comparison Using Heart Rate Variability

Use of virtual reality games in people with depression and anxiety

A novel Brain Computer Interface for classification of social joint attention in autism and comparison of 3 experimental setups: A feasibility study

Older Adults With Cognitive and/or Physical Impairments Can Benefit From Immersive Virtual Reality Experiences: A Feasibility Study

Extended Reality for Enhanced Telehealth During and Beyond COVID-19: Viewpoint, JMIR serious games

XR (Extended Reality: Virtual Reality, Augmented Reality, Mixed Reality) Technology in Spine Medicine: Status Quo and Quo Vadis

Augmented Reality in Medicine: Systematic and Bibliographic Review

Comparing acceptance and refusal rates of virtual reality exposure vs. in vivo exposure by patients with specific phobias

Virtual reality applications in mental health: Challenges and perspectives, Industrial psychiatry journal

Potential of virtual reality as a diagnostic tool for social anxiety: A pilot study

Action-Centered Exposure Therapy (ACET): A New Approach to the Use of Virtual Reality to the Care of People with Post-Traumatic Stress Disorder

Balancing User Privacy and Innovation in Augmented and Virtual Reality

Structured Model of Neurorehab: A Pilot Study of Modern Multitouch Technology and Virtual Reality Platforms for Training Sociocognitive Deficit in Children with Acquired Brain Injury

Serenity: A Stress-Relieving Virtual Reality Application based on Philippine Environmental Variables

Virtual reality as a distraction technique for pain and anxiety among patients with breast cancer: A randomized control trial

Design of a Virtual Reality System for Affect Analysis in Facial Expressions (VR-SAAFE); Application to Schizophrenia

A Comparative Study of Mental States in 2D and 3D Virtual Environments Using EEG

Thought Disposal: Co-Designing a virtual interaction to reduce stress in teens

The feasibility of an augment reality system to study the psychophysiological correlates of fear-related responses

Virtual reality and 360° panorama technology: a media comparison to study changes in sense of presence, anxiety, and positive emotions

A Novel Integrating Virtual Reality Approach for the Assessment of the Attachment Behavioral System

The effect of virtual reality technology on preoperative anxiety in children: a Solomon four-group randomized clinical trial

Functional co-activation within the prefrontal cortex supports the maintenance of behavioural performance in fear-relevant situations before an iTBS modulated virtual reality challenge in participants with spider phobia

Anxiety and threat magnification in subjective and physiological responses of fear of heights induced by virtual reality

Effectiveness of Self-guided App-Based Virtual Reality Cognitive Behavior Therapy for Acrophobia: A Randomized Clinical Trial

Van Straten, 0Phobia -towards a virtual cure for acrophobia: study protocol for a randomized controlled trial

Effectiveness of self-training using the mobile-based virtual reality program in patients with social anxiety disorder

PIANX@ A Platform for Piano Players to Alleviate Music Performance Anxiety Using Mixed Reality

Virtual Reality Cognitive Training Among Individuals With Alcohol Use Disorder Undergoing Residential Treatment: Pilot Randomized Controlled Trial

Attentional Bias, Alcohol Craving, and Anxiety Implications of the Virtual Reality Cue-Exposure Therapy in Severe Alcohol Use Disorder: A Case Report

Doc McStuffins: Doctor for a Day" Virtual Reality (DocVR) for Pediatric Preoperative Anxiety and Satisfaction: Pediatric Medical Technology Feasibility Study

Trash It, Punch It, Burn It -Using Virtual Reality to Support Coping with Negative Thoughts

Usefulness of the Mobile Virtual Reality Self-Training for Overcoming a Fear of Heights

Assessment of virtual reality as an anxiety and disgust provoking tool: The use of VR exposure in individuals with high contamination fear

Appropriate Number of Treatment Sessions in Virtual Reality-Based Individual Cognitive Behavioral Therapy for Social Anxiety Disorder

Salivary cortisol and cardiovascular reactivity to a public speaking task in a virtual and real-life environment

Design of a Physiology-Sensitive VR-Based Social Communication Platform for Children With Autism

E-virtual reality exposure therapy in acrophobia: A pilot study

Depression Prevention by Mutual Empathy Training: Using Virtual Reality as a Tool

A Fully-Immersive and Automated Virtual Reality System to Assess the Six Domains of Cognition: Protocol for a Feasibility Study

Use of virtual reality games in people with depression and anxiety

A Universe Inside the MRI Scanner: An In-Bore Virtual Reality Game for Children to Reduce Anxiety and Stress

Pengunaut trainer: a playful VR app to prepare children for MRI examinations: in-depth game design analysis

Virtual Reality MRI: Playful Reduction of Children's Anxiety in MRI Exams

Effects of robotic neurorehabilitation through lokomat plus virtual reality on cognitive function in patients with traumatic brain injury: A retrospective case-control study

Does raising heart rate prior to a behavioural test enhance learning in cognitive therapy for anxiety? An experimental test for the treatment of fear of heights using virtual reality

Head-to-Head Study of Virtual Reality Exposure Therapy for Posttraumatic Stress Disorder

Effects of Immersive Virtual Reality Content Type to Mindfulness and Physiological Parameters

Does virtual reality increase the efficacy of psychotherapy for young adults with mild-to-moderate depression? A study protocol for a multicenter randomized clinical trial

Abbas Bakhshipour Roudsari, Efficacy of Virtual Reality Based Worry Exposure Therapy on the Anxiety Severity and Worry in Generalized Anxiety Disorder

Effects of distraction using virtual reality technology on pain perception and anxiety levels in children during pulp therapy of primary molars

Claustrophobia Game: Design and Development of a New Virtual Reality Game for Treatment of Claustrophobia

Small-Group Technology-Assisted Instruction: Virtual Teacher and Robot Peer for Individuals with Autism Spectrum Disorder

A Novel Virtual Reality-Based Training Protocol for the Enhancement of the "Mental Frame Syncing" in Individuals with Alzheimer's Disease: A Development-of-Concept Trial

Influence of Interactive Questions on the Sense of Presence and Anxiety in a Virtual-reality Job-interview Simulation, Proceedings of the 2019 3rd International Conference on Virtual and Augmented Reality Simulations

Social Anxiety, Fear of Negative Evaluation, and Distress in a Virtual Reality Environment

Beat the Fear of Public Speaking: Mobile 360° Video Virtual Reality Exposure Training in Home Environment Reduces Public Speaking Anxiety

Do Trait Anxiety Scores Reveal Information About Our Response to Anxious Situations? A Psycho-Physiological VR Study, Proceedings of the 4th International Workshop on Multimedia for Personal Health & Health Care

A method of VR-EEG scene cognitive rehabilitation training

A Therapy System for Post-Traumatic Stress Disorder Using a Virtual Agent and Virtual Storytelling to Reconstruct Traumatic Memories

Olfactory Virtual Reality (OVR) for Wellbeing and Reduction of Stress

Virtual Reality Exposure Simulation for Student Veteran Social Anxiety and PTSD: A Case Study

Combined transcranial direct current stimulation with virtual reality exposure for posttraumatic stress disorder: Feasibility and pilot results

Head-Mounted Display-Based Application for Cognitive Training

Virtual Reality-Based Biofeedback and Guided Meditation in Rheumatology: A Pilot Study

The effectiveness of a virtual reality attention task to predict depression and anxiety in comparison with current clinical measures

A randomized controlled trial assessing the efficacy of a virtual reality biofeedback video game: Anxiety outcomes and appraisal processes

Remote Reminiscence Using Immersive Virtual Reality May Be Efficacious for Reducing Anxiety in Patients with Mild Cognitive Impairment Even in COVID-19 Pandemic: A Case Report

Using virtual reality-based training to improve cognitive function, instrumental activities of daily living and neural efficiency in older adults with mild cognitive impairment

The Effect of Hyperbaric Oxygen Combined with Virtual Reality Training on Oxidative Stress Indicators and Inflammatory Factors of Swimming Athletes Suffering from Depression

The Effect of Restorative Environment and Presence Based on Virtual Reality for Anxiety and Depression

Effectiveness of a stand-alone, smartphone-based virtual reality exposure app to reduce fear of heights in reallife: a randomized trial

Automated psychological therapy using immersive virtual reality for treatment of fear of heights: a single-blind, parallel-group

Treating patients with driving phobia by virtual reality exposure therapy -a pilot study

Effect of a Virtual Reality-Based Restorative Environment on the Emotional and Cognitive Recovery of Individuals with Mild-to-Moderate Anxiety and Depression

Automated virtual reality exposure therapy for spider phobia vs. in-vivo one-session treatment: A randomized non-inferiority trial

360° Video virtual reality exposure therapy for public speaking anxiety: A randomized controlled trial

Effectiveness of the Intent to Complete and Intent to Attend Intervention to Predict and Prevent Posttraumatic Stress Disorder Treatment Drop Out Among Soldiers

Virtual Therapeutic Garden: A Promising Method Supporting the Treatment of Depressive Symptoms in Late-Life: A Randomized Pilot Study

Virtual Reality Relaxation for Patients With a Psychiatric Disorder: Crossover Randomized Controlled Trial

Effectiveness of a smartphone-based, augmented reality exposure app to reduce fear of spiders in real-life: A randomized controlled trial

Mental Health and COVID-19: Early evidence of the pandemic's impact, Scientific brief

Mental health and the Covid-19 pandemic

A systematic review of immersive virtual reality applications for higher education: Design elements, lessons learned, and research agenda

Virtual reality as a clinical tool in mental health research and practice Dialogues in clinical neuroscience

Structured Model of Neurorehab: A Pilot Study of Modern Multitouch Technology and Virtual Reality Platforms for Training Sociocognitive Deficit in Children with Acquired Brain Injury

Anxiety and threat magnification in subjective and physiological responses of fear of heights induced by virtual reality

Virtual Reality for Supporting the Treatment of Depression and Anxiety: Scoping Review

Using Virtual Reality Exposure Therapy to Enhance Treatment of Anxiety Disorders: Identifying Areas of Clinical Adoption and Potential Obstacles

Virtual Reality Aided Therapy towards Health 4.0: A Two-Decade Bibliometric Analysis

The feasibility of an augment reality system to study the psychophysiological correlates of fear-related responses

The Effect of Restorative Environment and Presence Based on Virtual Reality for Anxiety and Depression

The effectiveness of a virtual reality attention task to predict depression and anxiety in comparison with current clinical measures

Nilufar Baghaei acknowledges the University of Queensland for the Startup Grant. Olatunji Omisore was supported by the Shenzhen Natural Science Foundation under the Grant #JCYJ20190812173205538.

None declared.

A summary of reviewed articles