Enhancing trauma treatment: Exploring working mechanisms and testing a novel route

The thesis covers three parts. The first part is aimed at testing a specific component in a treatment protocol; the 'Positive Closure' procedure in the Dutch EMDR protocol. In this procedure, the activation of a positive verbal statement was combined with the making of eye movements, although it had never been investigated whether these eye movements actually had a positive effect on those verbal statements. In three studies, set out in the thesis, no positive nor a negative effect of the eye movements in the procedure was found. The second part of the thesis concerns research into EMDR's working mechanisms and the use of modality-specific taxation in EMDR treatment. EMDR usually aims at making visual aversive memories less emotional by recalling a visual memory and simultaneously perform a dual task. The two tasks - recall and the other dual task (most commonly making horizontal eye movements) - compete for working memory capacity and the aversive memory is affected by this. A recalled memory becomes labile and when dual tasking is performed during recall of an aversive memory this memory generally becomes less emotional. In two studies Suzy and colleagues show that not only visual but the emotionality of auditory aversive memories can also be made less aversive. This was investigated in PTSD patients, and also in psychotic patients in whom an aversive auditory hallucination memory was processed. A modality-specific effect (i.e., a greater effect on emotionality decrease of the memory by using taxation in the same modality [auditory/visual] as the content of the memory [auditory/visual]) was not found. However, experimental research with healthy participants shows that an auditory dual task during the retrieval of auditory memories and a visual dual task during retrieval of a visual memory is more taxing than performing these two tasks cross-modal (i.e., the opposite modality). Since larger dual task loads are more effective in degrading emotionality of memories it is therefore potentially more effective to use a dual task matched in modality than taxing in the opposite modality during recall. A cautious conclusion is that in addition to a large effect of general taxation during memory recall, there is a smaller modality-specific effect. The third part of the thesis investigated a new form of trauma treatment, Visual Schema Displacement Therapy (VSDT). This form of treatment was tested in two analogue studies in which VSDT was compared to an abbreviated EMDR protocol and a control condition. In both studies VSDT and EMDR were superior to the control condition in reducing emotional disturbance, and VSDT was superior to EMDR. Results were maintained at follow up. VSDT and EMDR outperformed the control condition in terms of reducing vividness