Ires Ghielen

113 Meta-analyses on psychotherapies in MS and PD population is best represented in these meta-analyses, including fifteen RCTs of which eight were included in the first meta-analysis. The second meta-analysis included only studies in MS populations. Overall, the mean age of MS patient groups was lower compared to the PD patient groups. One can imagine that having a progressive neurological disorder in an earlier or later phase of life results in different psychosocial issues and cognitive abilities to benefit from therapy. A considerably large effect size was found in the pilot study of Okai and colleagues [41]. In this study, all PD patients additionally suffered from impulse control disorders. When the treatment components were critically investigated, it was notable that this was the only CBT-based intervention that included executive dysfunction education. PD patients often show an impairment in executive functioning in an early stage of the disease [56, 57]. Since this study showed a great improvement in psychological distress, this might indicate that executive dysfunction plays an important role in regulating negative emotions and cognitions, at least in PD patients with impulse control disorders. This, however, needs confirmation in future research. The pilot study by Kiropoulos et al. [35] also showed a large effect size ( g = 1.64). This study included newly diagnosed MS patients (< 5 years since diagnosis) and the age of these patients was lower compared to other studies that investigated MS populations. These patients might be less severely affected compared to other study populations. Comparisons, however, could not be made since studies reported different measures of disease severity. No differences were found concerning treatment components when compared with other CBT-based interventions in MS. Of great importance is the focus of the treatment types and control conditions. The studies by Ghielen et al. [40], Oreja-Guevera et al. [48], and Nordin et al. [47] investigated MBTs. These three studies showed (non-significant) negative effect sizes of g = -0.45, g = -0.37, and g = -0.10, respectively, favoring the control condition in reducing psychological distress symptoms. These studies all included an active form of control condition: physical therapy (TAU), psycho education, and relaxation, which might have diminished the positive effect. Besides this, the focus of ACT is not on symptom reduction but on coping with the disease despite of the symptoms that are present. This is achieved by improving awareness of ones bodily sensations, thoughts and feelings. As one can imagine, when one is more aware of his/her symptoms, these will also be more often reported, resulting in a higher score on questionnaires. 6