Efficacy of Virtual Reality Exposure Therapy in the
Treatment of PTSD: A Systematic Review
Raquel Gonc ¸alves1*, Ana Lu ´cia Pedrozo1, Evandro Silva Freire Coutinho2, Ivan Figueira3, Paula Ventura3
1Institute of Pschology, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, 2Department of Epidemiology, Escola Nacional de Sau ´de Pu ´blica (ENSP-FIOCRUZ),
Rio de Janeiro, Brazil, 3Institute of Psychiatry, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
The use of Information and Communication Technologies, such as virtual reality, has been employed in the treatment of
anxiety disorders with the goal of augmenting exposure treatment, which is already considered to be the first-line
treatment for Post-traumatic Stress Disorder (PTSD). To evaluate the efficacy of virtual reality exposure therapy (VRET) in the
treatment of PTSD, we performed a systematic review of published articles using the following electronic databases: Web of
Science, PubMed, PsycINFO, and PILOTS. Eligibility criteria included the use of patients diagnosed with PTSD according to
DSM-IV, the use of cognitive behavioral therapy (CBT) and the use of virtual reality for performing exposure. 10 articles were
selected, seven of which showed that VRET produced statistically significant results in comparison to the waiting list.
However, no difference was found between VRET and exposure treatment. Of these 10, four were randomized, two were
controlled but not randomized and four were non-controlled. The majority of the articles used head-mounted display virtual
reality (VR) equipment and VR systems specific for the population that was being treated. Dropout rates do not seem to be
lower than in traditional exposure treatment. However, there are a few limitations. Because this is a new field of research,
there are few studies in the literature. There is also a need to standardize the number of sessions used. The randomized
studies were analyzed to assess the quality of the methodology, and important deficiencies were noted, such as the non-use
of intent-to- treat-analysis and the absence of description of possible concomitant treatments and comorbidities.
Preliminary data suggest that VRET is as efficacious as traditional exposure treatment and can be especially useful in the
treatment of patients who are resistant to traditional exposure.
Citation: Gonc ¸alves R, Pedrozo AL, Coutinho ESF, Figueira I, Ventura P (2012) Efficacy of Virtual Reality Exposure Therapy in the Treatment of PTSD: A Systematic
Review. PLoS ONE 7(12): e48469. doi:10.1371/journal.pone.0048469
Editor: Mel Slater, ICREA-University of Barcelona, Spain
Received June 26, 2012; Accepted September 25, 2012; Published December 27, 2012
Copyright: ? 2012 Gonc ¸alves et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The study was partially supported by CNPq (Brazilian Research Council). No additional external funding was received for this study. The funders had no
role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: firstname.lastname@example.org
Post-traumatic stress disorder (PTSD) involves a constant feeling
of fear generated by inadequate consolidation of the autobio-
graphical trauma memory . Foa & Kozak  suggested that for
there to be adequate processing of the traumatic memory and the
consequent extinction of the fear, the memory must be activated
and safe components must be inserted. Prolonged Exposure
Therapy, proved to be highly eficacious in the treatment of PTSD,
aims to access the traumatic memory, including information about
the traumatic situation and related emotions, thoughts and
behaviors. It helps the patient to understand the context of the
traumatic experience as well as its impact in the patient’s life. It
also enables the patient to achieve a realistic perspective on the
traumatic event and its aftermath .
Despite the fact that exposure therapy stimulates emotional
engagement during imaginal exposure, some patients find it
difficult to immerse themselves in the traumatic scene and,
therefore, may quit the treatment. In some studies, dropouts and
non-response rates may reach 50% of the cases . Therefore, the
use of Information and Communication Technologies may
facilitate exposure for avoidant patients.
In this sense, virtual reality has been used as a tool for exposure
and has achieved positive results in the treatment of various
anxiety disorders including specific phobias, social phobia, panic
disorder and PTSD . Even though this resource has encoun-
tered some difficulties because it raises questions about affecting
the therapeutic relationship and struggles with personalizing
exposure for individuals with different traumas , its use has
yielded many benefits. Virtual reality exposure therapy (VRET)
facilitates the emotional engagement of patients with PTSD during
exposures to the multiple sensory stimuli made possible by the
virtual environment, bypassing symptoms of avoidance and
facilitating control on the part of the therapist [6–7]. The sense
of presence provided by a virtual environment that is rich in
sensory stimuli facilitates the emotional processing of memories
related to the trauma . This technological apparatus allows
gradual exposure to the feared environment according to the
needs of each patient. In addition, it can be used in situations
where time is limited, as well as in situations that are difficult to
control or unpredictable  or that could put the patient at risk if
the exposure were performed in a real situation. Finally, exposure
in a virtual reality environment allows for greater methodological
rigor in clinical studies as it allows for the standardization of the
duration and type of exposure for all patients .
The objective of this article is to conduct a systematic review of
studies that have used virtual reality in the treatment of PTSD. We
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aim to verify the efficacy of Virtual Reality Exposure Therapy for
patients diagnosed with PTSD.
We performed an electronic search in the following databases:
ISI/Web of Knowledge, PUBMED/MEDLINE, PILOTS and
PsycINFO in May 2011 with keywords that included the terms
PTSD OR ‘‘stress disorder*’’ and ‘‘virtual reality’’. In the ISI/
Web of Knowledge, we restricted the search criteria to include
only ‘‘articles’’ and ‘‘notes’’. Articles found in the references of the
articles selected for this review were also considered for analysis.
Independently data collection process was applied. The articles
included in the final selection had to fulfill the following criteria.
Criteria for inclusion: the use of patients diagnosed with PTSD
according to DSM-IV, the use of cognitive-behavioral therapy
(CBT) and the use of virtual reality for performing exposure.
Criteria for exclusion: theoretical articles, reviews, theses,
dissertations and book chapters, articles not published in a peer-
reviewed journal, articles that used patients who were not
diagnosed with full PTSD or techniques that were not part of
the repertoire of CBT, case studies, articles that did not include
outcome criteria and trials published in languages other than
English, Portuguese or Spanish.
After the search phase, we did an analysis of the methodological
quality of the randomized controlled trials based on the Cochrane
Collaboration Tool for Assessing the Risk of Bias . This tool
analyzes the risk of bias for each study that might interfere with the
results. In addition, six items were added that also represent risks
for biased results. These items were based on the scale developed
by Kocsis et al  and include description of relevant
comorbidities; information on screened, included and excluded
subjects; description of treatment (or reference); description of
concurrent treatment; an intent-to-treat analysis; and description
The final result of the search can be observed in the flowchart
Of the 300 articles obtained through the electronic search
summed from all the databases searched, 27 were excluded for
using samples including non-PTSD disorders or using patients
with subclinical PTSD, 36 were excluded for being case studies,
192 were excluded for being theoretical articles, reviews or trials
that did not include CBT, two were excluded for using outcome
measures that did not include symptoms of PTSD and seven were
excluded for using a sample compiled and used in a later study.
Thus, 10 articles were considered for the final analysis. This count
includes articles found in more than one electronic database,
which were, therefore, repeated. Additionally, some studies met
more than one exclusion criterion. Each of the studies selected is
Ready et al  performed an open trial with 21 Vietnam
veterans. The final result combined the samples with those from
an earlier study by Rothbaum et al , that consisted of a sample
of five participants. Nine patients in the most recent study
completed the treatment, and six patients dropped out during it.
Of the 21 initial participants, 14 completed at least one post-
treatment assessment. The questionnaires used included the
Clinician Administered PTSD Scale (CAPS), Impact of Events
Scale (IES), Beck Depression Inventory (BDI) and Subjective Units
of Discomfort Scale (SUDS). The protocol included 8 to 20 weekly
sessions, and each lasted 90 minutes. The techniques used
included psychoeducation, anxiety management techniques,
exposure using VR and imaginal exposure. Follow-ups were
performed at three and six months. There was a significant
reduction in total CAPS and IES after treatment and during the
follow ups. However, for the intrusion cluster on the CAPS scale,
no statistical significance was observed at the first measure post-
treatment; however, at the follow-ups, there was significant
improvement compared to the beginning of treatment. Although
there was a significant reduction in BDI during post-treatment and
at the follow-up at six months, this was not evident at the three-
month follow-up. Gains were maintained for 10 of the eleven
patients who completed all of the follow-ups.
Difede et al  evaluated the efficacy of treatment with VRET
in-patients who developed PTSD after the terrorist attack on the
World Trade Center. The participants were assigned to two
groups. In the first group, thirteen patients underwent intervention
with VRET, and eight matched subjects were assigned to the
waiting list. Five of the thirteen participants in the first group were
resistant to previous treatments, and four were resistant to
imaginal treatment. Because it was decided that these patients
would be assigned to treatment, the study became quasi-
experimental. The participants in the VRET group were paired
with the participants on the waiting list according to the severity of
their CAPS scores and socio-demographic characteristics. The
study sample was composed entirely of males with severe PTSD.
In addition to the use of CAPS, the participants were evaluated by
an independent assessor using BDI and Clinical Global Impression
(CGI). The treatment combined CBT with VR using techniques
including psychoeducation, relaxation training, cognitive restruc-
turing and VRET. The number of sessions was less than 14, with
a mean of 7.5. All of the patients received at least six weeks of
VRET. The results showed that nine of the 10 participants who
completed the training obtained clinically and statistically signif-
icant improvements. A large effect size was obtained (Cohen’s
d=1.54). Compared to the waiting list, the group treated with
VRET demonstrated statistically significant improvement based
on the CAPS score. The same did not occur for BDI and CGI, for
which an interaction between time and group was not noticed.
However, the authors stated that the baseline scores were low. At
the end of the study, six of the 10 participants in the VRET group
no longer met the diagnostic criteria for PTSD. Three patients
from the group undergoing VRET did not complete the
treatment, and one dropped out due to the anxiety related to
the exposure. The dropout rate in the control group was not
reported. The results remained the same in the follow-up at six
Wood et al  examined the effects of VRET on twelve
participants in a non-controlled study. 10 sessions that lasted 90 to
100 minutes each were performed once or twice a week. The Post
Traumatic Stress Disorder Checklist (PCL-M), the BAI and PHQ-
9 questionnaires were used. The techniques and procedures used
in the study included psychoeducation, meditation for anxiety
management, cognitive restructuring, biofeedback training and
gradual exposure using virtual reality. There was a significant
reduction in the PCL in 75% of the participants, and these cases
no longer fulfilled the criteria for PTSD. The study did not report
if there were dropouts over the course of the treatment, as well as
averages or standard-deviations and only showed the results with
a graph. The study did not perform a follow-up. The focus of this
article was on the cost-benefit analysis of using VR; thus, the
article may be limited in terms of methodology.
A randomized study by Ready et al  compared VRET with
Therapy Centered on the Present (TCP) in patients who are
veterans of the Vietnam War. Of eleven male participants, nine
completed the treatment, with five in the VRET group and four in
Efficacy of VRET for PTSD: A Systematic Review
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the TCP group. Protocols for both treatments consisted of 10
sessions. The CAPS and BDI scales were administered before and
after treatment and during a follow-up six months later by an
independent assessor who was unaware of the treatment. There
was an improvement of symptoms in both conditions from
pretreatment to post-treatment and at the follow-up, performed six
months after the end of the study, with scores on the CAPS scale
showing greater variations for VRET. However, there was not
a statistically significant improvement on the CAPS and BDI scales
either within or between groups. It was not possible to compare
and find statistically significant differences due to the small sample.
There were two dropouts, one from each group.
Roy et al  studied soldiers diagnosed with PTSD using
functional magnetic resonance imaging (fMRI) in addition to
evaluating the effects of VRET. In the first phase of the study,
there were 29 subjects who were assigned to four groups: fifteen
with both PTSD and Traumatic Brain Injury (TBI), nine with
PTSD only, one with TBI only, and four controls. The fMRI was
performed before and after treatment and during follow-up
periods. In the treatment phase, fifteen participants with PTSD
were initially selected at random for VRET (seven) or for
Prolonged Exposure (eight). At least twelve sessions lasting
90 min were performed over $ six weeks. Both the PE and
VRET treatments used psychoeducation, relaxation techniques
and some elements of imaginal and in vivo exposure. The groups
received equivalent times of exposure (with VR or imaginal
exposure), which lasted up to half of each session. The CAPS,
PCL-M and BDI scales were administered at the same time as the
cerebral scans. It was an ongoing study in which eight participants
with PTSD had completed the final scan, and six had dropped out.
As the authors considered the number of participants in each
group insufficient for a comparison of the efficacy of treatments,
the results of the two groups were combined, meaning, in this
respect, that the study was non-controlled. There was a non-
significant improvement in the clinical symptoms, which could be
measured through reductions in CAPS, PCL, CGI and BDI. The
results were maintained in the follow-ups performed at one, two
and three months with eight patients with PTSD completing the
post-treatment scan (five with both PTSD and TBI and three with
PTSD only). The brain regions of interest were the amygdala, the
hippocampus and the anterior cingulate cortex. Significant
improvements are evident on the fMRI scans, which showed
a reduced activation of the amygdala, subcallosal gyrus and lateral
prefrontal cortex as well as a less-accentuated reduction for the
anterior cingulate cortex. These results are corroborated by CGI
scores; however, the CAPS score improvements are not statistically
The study by McLay et al  is a controlled non-randomized
study that shows the results of treatment for PTSD in soldiers from
the Iraq War, all male. They compared six cases treated with
VRET and four cases with traditional exposure therapy. The
treatments were conducted once or twice per week, and the
number of sessions varied between six and twelve. There was no
standardization in the administration of the techniques or in the
number of sessions. The patients were treated according to the
clinical judgment of what they required, and they typically
Figure 1. Flowchart of the process of identifying and selecting studies.
Efficacy of VRET for PTSD: A Systematic Review
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received the treatment to which they were assigned. The scales
administered included PCL-M, CAPS, PHQ-9 and BAI. All of the
patients who were treated with VRET significantly reduced their
scores on the PCL-M (by 67% on average), BAI and PHQ-9. At
the end of the treatment, five no longer met the diagnostic criteria
for PTSD. The patients who received traditional exposure therapy
also showed statistically significant improvement at the end of the
treatment (a 74% decrease on the PCL-M), and none showed the
diagnostic criteria for PTSD at this stage. There was no statistically
significant difference between the treatments. The study didn `t
perform a follow up. There were no dropouts.
Rizzo et al  conducted an open trial with 40 war veterans
who were resistant to pharmacological treatment and counseling
using virtual Iraq. Sessions lasting 90 to 120 minutes were held
twice per week for five weeks. The average number of sessions was
less than 11. The techniques used included psychoeducation,
anxiety management techniques and imaginal, in vivo and VR
exposure. Participants were evaluated based on the PCL-M, BAI
and Patient Health Questionnaire (PHQ-9), in addition to
physiological monitoring, which included heart rate, galvanic skin
response and respiration frequency. However, the results of the
psychophysiological monitoring were not reported. A follow-up
was performed at three months. Of the 20 participants who
completed the treatment, there was a clinical and statistically
significant reduction in the PCL-M, with 17 participants showing
a reduction of more than 50%. Furthermore, sixteen of the
participants did not fulfill the criteria for PTSD after treatment.
When looking at the average scores for the BAI and the PHQ-9,
there was a statistically significant reduction at the end of
treatment. Half of the patients did not complete the treatment.
Seven soldiers dropped out before the first session, six quit after
the first session, and seven at the beginning of the VR treatment.
Gains were maintained at follow-ups.
The study by Botella et al  included subjects who had
experienced a broad variety of traumatic events and used
EMMA’s World as a VR tool. This system used symbols to
represent various traumatic events. Their sample included eight
men and two women. This was a randomized clinical trial with
two groups that used VRET or CBT with in vivo and imaginal
exposure. Participants on the waiting list were not included. The
study included 10 participants. The authors did not report the
number of participants in each group or whether any participant
did not complete treatment. Both protocols used from nine to
twelve sessions. There was a statistically significant reduction on all
the scales administered (CAPS, Davidson Trauma Scale (DTS)
and Posttraumatic Cognitions Inventory (PTCI) between pre- and
post-treatment conditions for the group that received VRET.
VRET proved to be more effective than traditional therapy on the
CAPS scale, but the difference was not statistically significant for
the CAPS scale or for the others administered. The researchers did
not perform follow-ups and did not report the dropout rate for
either of the groups.
The study by Gamito et al  evaluated VRET as an
alternative procedure for reducing symptoms of chronic PTSD in
elderly Portuguese veterans who had participated in the colonial
war in Africa. 10 participants, all male, were randomly assigned to
three groups: five for VRET, two for imaginal exposure, and three
for the waiting list. The protocols for VRET and imaginal
exposure were based on cognitive desensitization with twelve
sessions of exposure with virtual reality for VRET and twelve
sessions of traditional imaginal exposure for imaginal exposure
group. The first session for both protocols was dedicated to
psychoeducation. The CAPS, Impact of Events Scale Revised
(IES-R), Symptoms Checklist Revised (SCL-90-R) and BDI scales
(only for the VR group) were administered before and after
treatment. There was no statistically significant difference in the
analysis of the CAPS scale. However, the group treated with
VRET obtained a reduction of 8% when measured with CAPS,
although there was only a reduction of 1% for the group assigned
to imaginal exposure and 6% for the WL. There was a reduction
in IES-R for the group with VRET, whereas an increase was
observed for the other two groups. There was a significant
reduction in symptoms of depression (reduction of 40% on the
BDI) and on the SCL-90-R for the VRET group. No follow-up
was performed. One dropout was reported in the VRET group,
and the dropout rate in the control group was not reported.
The study by McLay et al  evaluated the efficacy of VRET
in the treatment of 20 Active Duty military personnel in
a randomized trial. 10 of these patients were assigned to VRET
and 10 to treatment as usual (TAU). The participants of the latter
group received a combination of typical treatments for PTSD,
which included Prolonged Exposure, Cognitive Processing Ther-
apy, Eye Movement Desensitization and Reprocessing, group
therapy, psychiatric medication, substance rehabilitation and
inpatient service. The VRET protocol included sessions of
psychoeducation, relaxation, attentional and autonomic control
training and exposure to a VR simulation of Iraq or Afghanistan.
There was no standardization of the treatment protocol, and the
number of sessions varied from 10 to 13 weekly sessions for the
two groups. The participants were monitored using the CAPS
scale before and after treatment. At the end of the treatment, seven
of the 10 participants in the VRET protocol showed improve-
ments of greater than 30% on the CAPS scale, whereas only one of
the nine participants who completed the TAU showed an
improvement greater than 30%. Both treatments showed efficacy
and there was no statistically significant difference between the
groups. Only one dropout in the TAU group was reported. The
researchers did not perform a follow-up.
Figures 2 and 3 summarize the different aspects concerning the
methodological quality of the randomized studies. Among these
investigations, only one study reported the method used for
generating the random sequence and whether the method used to
hide the sorting did not allow a prediction of the distribution of the
patients into groups. Two of the studies did not use a blind
evaluator; one did not report on this, and one made use of a blind
evaluator. In addition, only one of the studies included data for all
the subjects in the final analysis. In all of the articles, the main
scales were also administered at the final evaluation. In one study,
the presence of comorbidities was not described, and in three
studies, they were partially described. The numbers of subjects
screened, included and excluded were described completely in
only one study. In three studies, the treatments were sufficiently
described or referenced to allow replication. Only two studies
clearly provided information on concurrent treatments allowed
and administered during the course of the study, and they did not
permit concomitant treatments. In one study, this description was
partially completed, and in another study, there was the possibility
that the participants in group therapy were concurrently taking
non-stabilized psychotropic medication. None of the articles
performed an intent-to-treat analysis because there were no
evaluations over the course of treatment. In fact, there were only
pre- and post-treatment evaluations.
To the best of our knowledge and despite the current relevance
of this subject, this is the first systematic review that evaluates the
Efficacy of VRET for PTSD: A Systematic Review
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efficacy of VRET focused exclusively on patients diagnosed with
PTSD. A study conducted by Meyerbroker & Emmelkamp 
included a systematic review of VRET in various anxiety disorders
including PTSD. However, only two studies were considered in
their analysis [7–13]. A meta-analysis was performed by Parsons
et al , and two studies with PTSD were selected. The meta-
analysis was based on fewer than 20 subjects. Two different meta-
analyses in VRET and anxiety disorders were published [23–24],
including only one paper in PTSD . The lack of systematic
reviews and meta-analyses on the subject is probably due to the
small number of studies in the literature that use VR as a tool for
exposure. However, the few published studies are recent, with the
first dating from 2006 , which indicates rapid growth in this
Based on the evaluations of the 10 studies, the results point to
the potential efficacy of VRET in the treatment of PTSD. Among
the six studies that included a control group, a statistically
significant reduction in questionnaires evaluating symptoms of
PTSD was observed in four. In comparison to the waiting list,
results were significantly better for VRET. However, no difference
was found between VRET and exposure treatment. The same
result was obtained in the meta-analyses on the efficacy of VRET
and classical cognitive-behavioral evidence-based treatment in the
treatment of anxiety disorders, performed by Opris & colleagues
. We cannot discard, nonetheless, the possibility of a Type 2
error due to low sampling power; that is, if the samples were
larger, a difference in efficacy in favor of one of the treatments
might have been found. In three of the four non-controlled studies,
VRET showed efficacy, which confirms the potential efficacy of
Eight of the 10 studies used samples of war veterans. The high
utilization of this population was probably due to the high
financial and social costs of wars in terms of the number of soldiers
who return home with PTSD . In two studies, samples
included victims of various traumas, and the remaining study was
conducted with victims of the terrorist attack of September 11,
2001. War veterans are considered to be a more resistant sample7.
Thus, the results obtained might have been even more promising if
the studies had used subjects exposed to other types of trauma. A
problem involved in using VRET in comparison to traditional
exposure is related to the difficulty of constructing a context that
refers precisely to the traumatic memory of the patient . Due to
its high financial cost, it would be almost impossible to follow the
idiosyncratic method, which means personalizing the virtual
environment according to the perspective of each patient related
to the trauma. By contrast, with a homogeneous sample, only
some stimuli elicited by the virtual environment are necessary to
produce anxiety sufficient for activation of the traumatic memory
. In a study which used individuals that had suffered various
types of trauma , the virtual environment was even more
general, but it still evoked recollections of the traumatic event.
Figure 2. Methodological Analysis of Randomized Controlled
Trials; + + Low Risk of Bias; – High Risk of Bias; ? Unclear Risk of
Figure 3. Methodological Analysis of Randomized Controlled Trials.
Efficacy of VRET for PTSD: A Systematic Review
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The number of sessions varied between 5 and 20. Only four
studies set a fixed number of sessions. The others proposed only
a minimum number that could be exceeded depending on the
needs of the patient. The lack of standardization makes it difficult
to evaluate the efficacy of the protocol, although it is understand-
able considering that these were the first studies to test the efficacy
of VRET in the treatment of PTSD. Therefore, there is no
standard to follow. The sessions basically consisted of techniques
that included psychoeducation, anxiety management (such as
diaphragmatic breathing, progressive muscle relaxation and
meditation) and in vivo and imaginal exposure. Only three studies
reported using cognitive restructuring [13,14–21].
The majority of the articles used head-mounted display VR
equipment and VR systems specific for the samples. Only one
study used an automatic virtual environment, an adaptive VR
display called EMMA’s World . This system allows for deep
immersion into the virtual environment for both the patient and
the therapist, which offers a better perception of what the patient is
seeing. This VR equipment is non-specific, and different
environments could bring the patient into contact with different
feelings that serve as triggers for traumatic memories. No other
studies used the automatic virtual environment methodology. So,
it was not possible to test which of the two methodologies was
more efficacious in the treatment of PTSD.
Randomized clinical trials.
randomized studies were not conducted in accordance with
rigorous criteria for quality. All of them had methodological
limitations that introduced a risk of bias for the final results. Proper
reporting of the items that constitute a randomized trial assists in
the critical evaluation of internal validity and the generalization of
the results .
It is striking the absence of information to judge the quality of
the trials. The majority of studies omitted data concerning random
sequence generation, allocation concealment, description of
relevant comorbidities, information on screened, included and
excluded subjects and description of incomplete outcome data.
Besides, even in the study with the higher amount of items
evaluated favorably , those items account for less than half of
the total of the evaluated items. The items with the lower risk of
bias were selective reporting and description of treatment.
Another serious limitation concerns the use of extremely small
samples in each of the randomized trials. For example, two studies
[19–20], despite being randomized, involved only 10 participants
each. The randomized study with the largest sample included 20
subjects . These small samples make a meta-analysis focused
on those data impossible. Finally, the absence of effect size makes
it difficult to understand to what extent the result is explained by
the predictor variable . In addition, none of the studies used
the number needed to treat (NTT), which is a more powerful and
intelligible statistical tool because it establishes the necessary
minimum number of individuals to be treated in the event that one
of them no longer fulfills the diagnostic criteria after the treatment
Future studies should take into account the methodological
issues mentioned above and presented in figures 2 and 3 in order
to improve the quality of the trials in VRET.
We observed an absence of key information that
is required to understand the evaluation of VRET efficacy because
some studies focused on the description of the VR system
configured for exposures, thereby placing less emphasis on
evaluating the efficacy of the treatment. Some studies did not
We found that the four
even present quantitative results but only qualitative information
about efficacy [14–18].
In spite of these limitations, all of the articles reported the results
of the most important scale at the final evaluation. Therefore,
there was no risk of hidden possible negative results. In addition,
half of the articles performed follow-ups. Those data were
collected from one month to one year after the end of treatment.
Although the ideal time suggested for a follow-up begins at twelve
months , the fact that there was follow-up assessment shows an
effort to incorporate a more robust methodology. We believe that,
with advances in the study of VRET efficacy in the treatment of
PTSD, future studies will achieve better methodology quality.
Another important consideration is treatment adherence. It is
known that exposure techniques can have a high rate of non-
adherence due to the initial worsening of the symptoms. For there
to be extinction of the fear associated with the memory of the
traumatic event, it is necessary for the patient to experience
anxiety and feel its reduction after a specified period of repetition
of the traumatic memory. Because the technique is highly
anxiogenic, many patients do not agree to undergo the treatment
or give up at the beginning of treatment. Theoretically, VRET
appears to partially bypass this problem by providing exposure in
a more controlled and safer environment. However, except for two
studies [17–21], there were dropouts from the VRET group for all
of the studies that supplied this information. Two studies did not
report the dropout rate [14–19]. The highest dropout rate
occurred in the study by Rizzo et al , where half of the total
sample of 40 participants did not complete the treatment. Two
other studies showed high dropout rates [16–7], with six dropouts
in each (out of 21 and 29, respectively).
It is important to mention the low treatment adherence rates
found in the active duty military populations. Out of 49,425
veterans diagnosed with PTSD, only 9.5% attended nine or more
VA mental health sessions in 15 weeks or less in the first year of
diagnosis . This population has issues regarding stigma
associated with mental health problems, higher rates of alcohol
related problems, and competing responsibilities for preparing for
the next deployment that have a dramatic negative effect on
adherence to treatment [29–30].
Despite the fact that exposure therapy is considered to be highly
aversive , in a study by Hembree et al , the dropout rates
for exposure therapy were not different from the rates found for
techniques considered to be less aversive, such as Cognitive
Therapy, Stress Inoculation Training and EMDR during the
treatment of PTSD. However, due to the high dropout rate that
was evident in the selected articles, we believe that there remains
a certain loss of control of anxiogenic stimuli during VRET. The
loss of control might be related to the need for the therapist or the
patient himself to manage the equipment so as to reduce the
intensity of the stimulus when anxiety is very high. The use of new
technologies, such as physiology-driven adaptive VR stimulation
that automatizes the system to make it less dependent on the
intervention of the psychotherapist during exposure, may be able
to bypass this limitation.
Finally, one potential application of VRET would be for
patients who are resistant to traditional exposure. For example,
Difede et al  included five patients who had not responded
initially to traditional exposure, and the results showed a positive
response to VRET (for three of them, there was a reduction of at
least 25% in CAPS, whereas for the other two, the reduction was
greater than 50%). Replicating this finding would provide
evidence of the mechanisms by which VRET could be more
advantageous than traditional exposure. We believe that the
results would be promising because VRET prevents patients from
Efficacy of VRET for PTSD: A Systematic Review
PLOS ONE | www.plosone.org6 December 2012 | Volume 7 | Issue 12 | e48469
using safety signals that make engagement difficult, which Download full-text
compromises the adequate extinction of conditioned fear.
The results of this systematic review suggest the potential
efficacy of VRET in the treatment of PTSD for different types of
trauma. VRET proved to be as efficacious as exposure therapy.
VRET can be particularly useful in the treatment of PTSD that is
resistant to traditional exposure because it allows for greater
engagement by the patient and, consequently, greater activation of
the traumatic memory, which is necessary for the extinction of the
However, there remains a vast field to be explored that requires
methodologically stronger trials and replications of those trials, the
standardization of treatment, empirical studies with different VR
systems and attempts to increase the rate of adherence to
treatment. In future studies, the use of VRET for traditional
exposure resistant patients would be interesting, as would the use
of artificial intelligence to make the system less dependent on the
intervention of the psychotherapist at the moment of exposure.
PRISMA 2009 Checklist.
Conceived and designed the experiments: RG ALP IF PV. Performed the
experiments: RG ALP. Analyzed the data: RG EC. Contributed reagents/
materials/analysis tools: RG EC. Wrote the paper: RG IF PV.
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