Metacognitive therapy vs. eye movement desensitization and reprocessing for posttraumatic stress disorder: study protocol for a randomized superiority trial

Posttraumatic stress disorder (PTSD) is a frequently occurring and often debilitating anxiety disorder resulting from exposure to trauma [1, 2]. Prolonged exposure therapy [3], trauma-focused cognitive behavioural therapy (CBT) [4] and eye movement desensitisation reprocessing (EMDR) [3] are recommended treatments for PTSD. Each of these approaches utilises exposure to trauma memories as one of the main components in the intervention. The efficacy of these treatments is supported by a large number of studies that show equivalent levels of outcome with no particular treatment evidencing superiority [4, 5]. However, it has been noted that EMDR has to some degree been compared to other active treatments for PTSD in rigorous controlled trials.

Although the majority of patients improve, a substantial proportion of patients drop out of treatment [4, 6, 7], present with residual symptoms following treatment or fail to improve [7‐9]. Approximately 37–51% of patients completing therapy improve significantly [8], which leaves substantial room for improving outcomes. Furthermore, a substantial portion of the clinical trials on PTSD have major methodological limitations [10].

EMDR is based on the assumption that posttraumatic symptoms are caused by traumatic experience(s) being stored in an unprocessed way disconnected from existing memory networks [11]. In EMDR the patient is asked to focus on trauma-related imagery, negative cognitions and body sensations while simultaneously focusing their attention on a bilateral physical stimulation. The procedure in EMDR is postulated to facilitate the processing of the traumatic memory into existing memory networks [11]. A number of theories explaining the potential mechanisms underlying the effects EMDR have been proposed (e.g. [12]). The importance of bilateral eye movements is often highlighted, but there is still substantial controversy about whether bilateral eye movements are of importance [13] or not [14‐16]. It is also important to note that dismantling randomized controlled trials comparing EMDR with and without bilateral eye movements does not in itself provide sufficient evidence on potential mediators and mechanisms for treatment outcome [17]. To the best of your knowledge, to date no RCTs have been conducted in EMDR that incorporate the investigation of potential mediators of treatment outcome as outlined by Kazdin [17, 18]. As such there is still a pressing need for trials investigating potential mediators of treatment outcome of trauma-focused treatments generally and EMDR specifically [19]. EMDR is usually considered an evidence-based treatment for PTSD [5, 8, 20].

Metacognitive therapy (MCT) [21, 22] is one of the more recent approaches in the treatment of PTSD. The focus of MCT is on removing specific barriers to spontaneous recovery that is purported to normally occur following trauma. Metacognitive beliefs are beliefs and theories people have about their thinking and how to regulate their thoughts. It could be beliefs that thoughts have a special meaning (sinful thoughts) or that thoughts may be harmful or uncontrollable. The metacognitive beliefs are hypothesised to underlie an unhelpful response style consisting of worry, rumination and threat monitoring, and other coping behaviours such as attempting to fill gaps in memory. These response styles prevent cognition and arousal returning back to basal levels of processing a threat-free environment. In effect PTSD symptoms are maintained because these factors prolong threat-related processing and interfere with the downregulation of subcortical arousal. In contrast to EMDR, MCT does not involve prescribed exposure exercises or restructuring of negative trauma-related memories.

MCT has been shown in early trials to be an effective, time-limited (8–10 sessions), well-tolerated and apparently highly effective treatment option for both recent onset and chronic PTSD [23‐26]. The core treatment has been investigated using an A-B direct replication series [23], an open trial [24] and a randomized controlled trial with delayed treatment as a control condition [25]. These preliminary results indicate that MCT is a well-tolerated treatment and that most patients experience significant improvements that are maintained at follow up. Furthermore, a clinical trial to compare MCT with prolonged exposure (PE) has shown that MCT performs better [26]. This trial demonstrated a statistically significant reduction in reported PTSD symptomatology, depression and anxiety symptoms post-treatment in the MCT group compared to the PE condition. In conclusion, MCT appears to be a highly promising treatment for PTSD, generating large clinically significant treatment effects for clients exposed to a range of traumatic experiences, which include accident survivors and assault and rape victims. However, to date no study has directly compared MCT with EMDR. The aim of the present study was to undertake such a comparison to determine the relative effectiveness for each of the treatments immediately following treatment and at 12-month follow-up.

The following aims and hypotheses were set up in the trial: (1) to evaluate the effectiveness of MCT compared with EMDR in PTSD using a comparative randomized controlled study; (2) to examine potential moderators and mediators of treatment outcome; (3) to examine and compare the relapse rate in MCT and EMDR.

The main hypotheses to be tested include the following: