COMISIÓN PLAN PRESUPUESTO

4.1.1 The relationship between presence and the outcome of treatment using IVR

Meta-analysis using seven studies (n = 311) found a small effect size for a relationship between presence and the outcome of treatment using IVR, r = .28, 95% CI [0.15, 0.39]. This showed that a greater level of presence during treatment using IVR was associated with better treatment response. As research in this field is in its infancy and limited the inclusion criteria for the review enabled all available data to be investigated. However, combining different statistical tests can introduce

confounds (Borenstein et al., 2009). So to check the finding was robust a second analysis was carried out using only studies reporting bivariate correlations (n = 184). This also showed a small effect size, r = .27, 95% CI [0.12, 0.40] and the result supports the initial finding. Two (Hoffman et al., 2008; Riva et al., 2008) of the five studies ineligible for meta-analysis also indicated that this relationship existed.

Presence is commonly assumed to be a key mechanism underlying IVR treatment efficacy (Spagnolli et al., 2014). The meta-analyses support this.

50 the relationship between presence and the outcome of treatment using IVR does not necessarily imply that these variables are causally related. Only two studies included in the analysis found such a relationship (Girard et al., 2009; Schneider & Hood, 2007). These studies received a weighting of 28.64 and 32.24 respectively in the initial analysis and the latter received a 61.54 weighting in the second analysis. The differences in the characteristics of the included studies and their findings supports the rationale for examining variables which potentially moderate this relationship.

4.1.2 Variables which potentially moderate the relationship between presence and the outcome of treatment using IVR

4.1.2.1 Clinical difficulty and IVR treatment type

Riva et al. (2008) was the only study to find a relationship between presence and the outcome of treatment using IVR whose participants suffered from anxiety. However, unlike the other studies investigating anxiety, participants in Riva et al.'s (2008) study did not meet DSM-IV criteria for an anxiety disorder and were treated for stress using IVR relaxation. The other studies indicating a relationship treated pain, symptom distress and tobacco addiction using IVR for distraction or to administer a therapeutic task.

This finding could partly relate to participants’ attentional focus during the treatment. Attention is required in order to experience a sense of presence (Witmer & Singer, 1998). Additionally, sustained attention during treatment is associated with improved treatment outcomes, whilst distraction during treatment is related to poorer treatment outcomes (Telch et al., 2004). It is possible that the more the individual directs their attention towards the VE, the less attentional capacity they

51 have available to process nociceptive signals or outside information (Cabas-Hoyos, Gutierrez-Martinez, Gutierrez-Maldonado, & Loreto, 2010; Hoffman et al., 2008).

IVR distraction is based on the premise that IVR exerts a powerful demand on attentional resources yet Hoffman et al. (2000) and Chan et al. (2007) did not find that presence was related to the outcome of treatment using IVR. However, the former study reported a trend towards this relationship. Chan et al. (2007) was the only study using just child participants. This may have affected their finding as children experience presence differently to adults (Triberti et al., 2014) and participants received parental support with filling out measures. Interestingly, nursing staff’s observations suggested that participants who appeared less present in IVR became distracted and anxious when medical treatment began.

VRET treatments were interrupted by the administrator which might have reduced participants’ attention towards the VE. The lack of relationship in VRET studies may also relate to Foa and Kozak's (1986) theory. This proposes that a phobic fear structure must be activated for emotional processing to occur. The importance of presence to elicit anxiety is supported by the finding that these factors are associated during the initial VRET session (Ling et al., 2014). However, once the fear structure is activated, controlled, prolonged, repeated exposure is required for habituation and extinction to occur. In support of this, research shows that greater time in VRET results in a more positive treatment outcome (Opriş et al., 2012; Powers & Emmelkamp, 2008). Therefore, presence may be necessary but insufficient by itself to lead to superior treatment outcome (Meyerbröker et al., 2011; Price & Anderson, 2007).

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4.1.2.2 Outcome measures

The majority of studies reporting a relationship only used domain-general measures. Therefore, presence in IVR may improve general psychological distress rather than targeting disorder-specific symptoms. However, data did not allow comparison of domain-specific and domain-general measures within studies to consider this finding independently of other between-study variations.

Different measures of presence did not seem to moderate the relationship. However, these measures are based on different constructs of presence, may lack sensitivity to the specificities of therapy using IVR (Spagnolli et al., 2014) and single-item measures may prevent a complete evaluation of the sense of presence (Triberti et al., 2014). Moreover, the ability of self-report questionnaires to capture the subjective experience of presence has been questioned (Slater & Steed, 2000; Slater, 2004). Therefore, this finding must be interpreted with caution.

4.1.2.3 Dose-response relationship

Studies indicating a relationship between presence and the outcome of treatment using IVR generally used shorter and fewer IVR treatment sessions. However, Girard et al.'s (2009) study and an initial study of multiple sessions of IVR distraction treatment (Hoffman et al., 2001) found improved treatment outcome and increased presence with repeated immersion. Therefore, other factors may account for the finding of the current review. These could include fun (Hoffman et al., 2008), enjoyment, successful task completion (Girard et al., 2009) and a pleasant emotional experience during IVR. It is possible that such factors may sustain and enhance attention, generating presence and leading to improved treatment outcome in certain treatments using IVR such as IVR distraction and relaxation. For VRET, the

53 theoretical rationale and research findings support a null finding for the relationship between presence and the outcome of treatment using IVR in relation to IVR dosage (Opriş et al., 2012; Price & Anderson, 2007).

4.1.2.4 Other moderating variables

Compared to studies which did not find a relationship, studies which indicated a relationship used participants with a higher mean age and had a higher percentage of Caucasian and female participants. Research in this field is limited with mixed findings (Ling, Nefs, Brinkman, Qu, & Heynderickx, 2013) making the implications of this data difficult to determine.

The median sample size was 53 for studies which indicated a relationship and 14 for studies finding no relationship. This may suggest that studies finding no relationship were under-powered. Whilst literature discussed above makes this seem unlikely for VRET studies, it could help explain Chan et al.'s (2007) and Hoffman et al.'s (2000) findings. It seems less likely that sample size impacts on the relationship between presence and the outcome of treatment using IVR as sample size varied from 11-107 in studies indicating a relationship.

Contrary to Ling et al. (2014), technology characteristics did not appear to moderate the relationship. This finding may be affected by the small number of studies in the review and the paucity of data reported in these studies.