Elsevier

Computers in Human Behavior

Volume 72, July 2017, Pages 371-380
Computers in Human Behavior

Review
Virtual reality exposure therapy in flight anxiety: A quantitative meta-analysis

https://doi.org/10.1016/j.chb.2017.03.007Get rights and content

Highlights

  • The effectiveness of VRET in flight anxiety was examined.

  • Findings provide arguments for the use of VRET for treating flight anxiety.

  • Quality trials, sample size, and number of exposures were significant moderators.

Abstract

Background

Flight anxiety and the fear-related avoidance draw serious personal and financial negative consequences. Although classical exposure techniques for flight anxiety are widely used, they involve significant limits. Efforts to develop the benefits and access to evidence-based psychotherapies have led to a new method of delivering exposure technique, namely virtual reality exposure therapy (VRET). Until now, there has been no meta-analysis which assumed as a primary objective the analysis of VRET effectiveness in flight anxiety.

Methods

The present meta-analysis aimed to investigate the efficacy of VRET interventions for flight anxiety compared to various control conditions, at post-test and follow-up. We conducted a quantitative review of 11 randomized studies, we examined potential moderators of the efficacy of interventions and we investigated the presence and the degree of publication bias.

Results

Results pointed out significant overall efficiency of VRET in flight anxiety at post-test and follow-up. Analysis highlighted the superiority of VRET vs. control conditions at post-test and follow-up and the superiority of VRET vs. classical evidence-based interventions at post-test and follow-up. Results revealed similar efficacy between VRET and exposure based interventions at post-test, and showed better treatment gains over time when using VRET vs. exposure based interventions. Moderation analyses revealed that low quality trials, with smaller and younger samples led to a larger effect size of VRET for flight anxiety. Also, outcome types, the number of exposure sessions and follow-up intervals were significant moderators of the efficiency of VRET in this disorder.

Conclusions

The present meta-analysis supports the efficiency of VRET in flight anxiety and encourages the use of this type of exposure both in clinical practice and research field.

Introduction

Flight anxiety affects approximately 10–40% of the general population (Dean and Whitaker, 1982, Van Gerwen and Diekstra, 2000). Among people who have anxiety to fly, about 20% use sedatives or alcohol to cope with anxiety (Howard et al., 1983, Wilhelm and Roth, 1997). Flight anxiety and the fear-related avoidance draw serious personal and financial negative consequences, such as professional repercussions, stigmatization (Baños et al., 2002), and significant financial reduction in airline revenue (i.e., 9% for the US airline industry in 1982, Dean & Whitaker, 1982). Although classical exposure techniques for flight anxiety, ‘in vivo’ and ‘in imago’ exposures, are widely used and effective treatments (Deacon and Abramowitz, 2004, Emmelkamp et al., 1985, Hodges and Rothbaum, 2000), they involve certain limitations: low control of the situation, confidentiality issues, financial and time costs, development of aversion or are dependent on the patient's ability to recreate the phobic stimulus (Emmelkamp, 2005, Rothbaum et al., 2000).

Efforts to develop the effectiveness, benefits, and access to evidence-based psychotherapies have led to a new method of delivering exposure technique, specifically, the use of virtual reality (VR; Da Costa, Sardinha & Nardi, 2008). VR is a new delivery tool for exposure techniques, using a computer-generated virtual environment, enabling systematic exposure to anxiogenic stimuli in a relevant context (Parsons & Rizzo, 2008). This new facility has a number of advantages compared to ‘in vivo’ and ‘in imago’ exposure techniques: is safer, can be repeated as often as needed, the therapist has better control over the content and exposure rhythm, exposure can be individualized, and it is cost effective for patients (Emmelkamp, 2005, Krijn et al., 2007).

Recent qualitative systematic reviews (Da Costa et al., 2008, Price et al., 2008) reporting case studies and controlled trials emphasize that virtual reality exposure therapy (VRET), with or without cognitive behavior therapy (CBT), is an efficient and effective treatment for flight anxiety, being comparable or superior to in vivo exposure, progressive muscle relaxation, cognitive therapy, bibliotherapy, or supportive group therapy.

Further, a recent meta-analysis (Opriş et al., 2012), comparing VRET with control conditions and classical evidence-based interventions in anxiety disorders, showed that VRET is efficient in reducing flight anxiety, compared to control conditions at post-treatment (two studies, D = 0.53, VAR D = 0.007). The same meta-analysis (Opriş et al., 2012) revealed a similar efficacy on the flight anxiety primary outcome measures (five studies, D = 0.40, VAR D = 0.21) and real-life impact outcomes (three studies, D = −.22, VAR D = 0.02) at post-treatment, between VRET and classical evidence-based interventions. Regarding the long-term efficacy, in case of fear of flying, VRET was superior to classical evidence-based interventions on primary and behavioral outcomes (three studies, D = 0.33, VAR D = 0.08).

Another meta-analysis (Parsons & Rizzo, 2008) which evaluated the magnitude of VRET related changes in six anxiety domains, revealed that VRET had statistically large effects on flight anxiety (four studies, D = 1.59, VAR D = 0.05).

Although the results of previous systematic reviews and meta-analysis (Da Costa et al., 2008, Opriş et al., 2012, Parsons and Rizzo, 2008, Price et al., 2008) gave us an overview of the efficacy of VRET in flight anxiety, these reviews are not updated, complex analyses were not performed and analyses made on this disorder are secondary objectives. Considering that research in the field of flight anxiety is in development, there is a need to outline a research line based on quantitative syntheses, to estimate a population effect size on independent studies. Until now, there has been no meta-analysis which assumed as a primary objective the comparison between the effectiveness of VRET and control conditions or classical evidence-based interventions in flight anxiety. Considering these needs and analyzing current methodological problems, the present meta-analysis tried to provide answers to the following questions: 1) What is the overall efficacy of VRET in flight anxiety?; 2) What is the efficacy of VRET compared to control conditions?; 3) What is the efficacy of VRET compared to classical evidence-based interventions, globally?; 4) What is the efficacy of VRET compared to exposure based interventions (i.e. classical interventions that include ‘in vivo’ or ‘in imago’ exposure techniques). Another objective of the present meta-analysis was to investigate potential moderators of the effectiveness of VRET.

Moderator variables were selected on the basis of prior research. Previous studies identified these variables as potential moderators of interventions efficacy/effectiveness in anxiety disorders. We are briefly discussing these moderators below.

First, we took into consideration the number of participants, participant's mean age and percentage of female participants as variables that can influence the effects of VRET. We anticipate that the effects of VRET will be larger in smaller and younger samples (Holzinger et al., 2011, Neguţ et al., 2016). Second, we considered that gender may influence the effect due to a greater number of women than men enrolled in studies (Krijn, Emmelkamp, Olafsson, & Biemond, 2004). Also, we considered the number of exposure sessions as a possible moderating variable due to large variations of exposure sessions number (Krijn et al., 2004) and the fact that this variable appears to influence the effect of treatments on anxiety disorders (Craske et al., 2008).

Further, the quality of randomized trials is an important variable that can impact on outcomes of interest (Kleijnen & Van Groenendaal, 2000). We assumed that low quality of randomized trials will lead to an increase in the effect size of the compared conditions. To assess the quality of randomized trials included in the present meta-analysis we used The Cochrane Collaboration's tool for assessing risk of bias (Higgins et al., 2011).

We analyzed the influence of outcome types on the overall effect size of VRET. Based on previous research on anxiety disorders we expected that VRET will have a higher efficiency on specific distress and behavioral level (Opriş et al., 2012). Moreover, there is a major difference between follow-up assessments in studies of flight anxiety. Therefore, we took into consideration the follow-up length variable to analyze its effects on results change. Moderation analyses with categorical variables were conducted by assuming independence of studies based on the moderators' categories.

Section snippets

Literature search

The systematic literature search has been conducted on the PsychInfo, ISI Web of Science, Scopus, PubMed and ScienceDirect databases, up to 30th of September 2015, using the following terms: “virtual reality” or “VR” in combination with “fear of flying” or “flight anxiety” or “flight phobia” or “flying anxiety” or “flying phobia” or “aviophobia” or “flight phobic” or “avoidance of flying” or “fearful flyers”. Also, in order to detect other studies, the references of recent studies and reviews

The overall efficiency of VRET

There were 16 effect sizes regarding the effectiveness of VRET at post-test and 15 at follow-up (see Table 2). The overall effect size of Hedge's g = 0.592 (95% CI [.327–.858], p = 0.00), revealed a medium and statistically significant effect size of VRET at post-test, with evidence of heterogeneity within results (Q(15) = 32.257, p = 0.00, I2 = 53.49).

Results showed a medium statistically significant effect size of VRET at follow-up (g = 0.588, 95% CI [.216–.960], p = 0.00). There was evidence

Discussion & conclusions

The present meta-analysis aimed at investigating the efficacy of VRET interventions for flight anxiety compared to control conditions and classical evidence-based interventions, at post-test and follow-up. We conducted a quantitative review of 11 randomized studies, we examined potential moderators of the efficacy of interventions and we investigated the presence of publication bias. Overall, findings from this meta-analysis provide arguments for the use of VRET for treating flight anxiety.

Limitations and future directions

Conclusions presented in this meta-analysis have several limitations. First, there were a limited number of studies included in the analyses which could lead to a weaker statistical power, and limited the conclusions that can be draw from these comparisons. This limit can be observed also from the moderation analysis performed as there were no sufficient studies to test for all the potential moderators. Therefore, further researches should analyze the effectiveness of VRET in flight anxiety,

Disclosure statement

No competing financial interests exist.

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