Discussion
depressive rumination, depressive, equanimity, MDD, depression
The purpose of this study was to investigate the efficacy and neural correlates of a MBERT in the treatment of depressive rumination. More specifically, we aimed to shed light on the neural mechanisms related to typical trained emotion regulation skills in CBT. To this end, 42 subjects suffering from MDD completed an eight-session treatment in which ER strategies were taught and practiced, while cortical blood oxygenation was assessed with fNIRS. We examined the efficacy of the training on a behavioral level using psychometric measures. Impacts of the training on a psychological and neural level were investigated using subjective ratings on session variables and hemodynamic responses during the training in the CCN. We found significant and treatment-specific changes in depressive symptom severity, self-compassion, self-efficacy and ruminative thoughts after completion of the MBERT in comparison to TAU. During and between training sessions, subjective ratings on burden, self-compassion, equanimity and effort changed significantly in expected change patterns, i.e. increases in self-compassion and equanimity and decreases in subjective burden and effort. The amount of implemented therapeutic techniques provided by the therapist between the trials of the training decreased during as well as between sessions, indicating that less therapeutic guidance was needed with ongoing treatment. Concerning the neural correlates, we found higher cortical activation during training compared to rest trials in the prefrontal areas of the CCN, namely in the bilateral DLPFC and the bilateral IFG. As hypothesized, this difference between conditions decreased significantly across sessions in the bilateral DLPFC with a linear decrease. However, no significant reduction of the condition contrast was found within each session. Finally, an exploratory analysis indicated associations of the individual cortical oxygenation in the CCN and process-related subjective ratings during the training. Individual fluctuations of CCN oxygenation above the individual mean at the beginning of the training was associated with reduced subjective effort and burden, as well as increased self-compassion and equanimity. However, with procession within each training session and between training sessions, remaining higher intra- und inter-subject levels of OAs the designed MBERT training is composed of typical CBT components, it is not surprising that the observed efficacy is well in line with previous studies, showing that CBT is an effective treatment of MDD (It is known from previous studies that there are differences in the epidemiology and the course of depression between sexes, both on a behavioral as well as a neural level (Some limitations have to be addressed. First of all, even though the training was found to be highly effective, we did not collect follow-up data to examine the long-term stability of the effects. At least the effects obtained seemed to remain stable over five weeks, as we could observe by the cross-over design in those subjects that first received the training. To verify long-term effectiveness, comprehensive follow-up surveys on a larger sample and after several months would be needed. However, it was not the aim of this study to create a new treatment method as a standalone treatment, but to primarily shed light on the mechanisms and neural correlates of CBT-specific treatment components. Second, it cannot be ruled out that patients may have been influenced in their subjective ratings and the answering of the psychometric questionnaires by the presumed expectations of the investigators (