D ISCUSSION OF THE R ESULTS

In the first study, female survivors of the ongoing war in Eastern Congo, who sought medical treatment, were interviewed regarding their traumatic experiences, shutdown dis-sociation, PTSD and depression symptoms. The results confirm that cumulative trauma ex-posure was associated with increased PTSD symptom severity. Consistent with many other studies, the number of self-experienced traumatizing events significantly predicted the se-verity of PTSD (e.g. Neuner et al., 2004). However, prior studies did not consider witnessed and self-experienced traumatizing events together in a composite model. The model suggests that the number of different traumatic event types that were self-experienced as well as the shutdown dissociation influenced separately the PTSD symptom severity. Witnessing trau-matizing events seem to raise the depression severity. Further the link between shutdown dissociation and PTSD symptoms yielded a strong relationship. This result is in line with previous studies finding correlation strengths ranged from medium to very large effect sizes (Briere et al., 2005; Murray et al., 2002; Nijenhuis, van der Hart, Kruger & Steele, 2004;

Weiss et al., 1995). Additionally, depressive symptoms were associated with the PTSD symptom severity. This finding argues for co-morbidity. Further shutdown dissociation was also related to greater symptom severity of depression. But the relationship between dissoci-ation and depression vanished when the PTSD symptom severity was considered. To con-clude, the findings emphasize the importance of shutdown dissociation in elevated PTSD and confirm that the trauma exposure, dissociation, PTSD and depression symptom severity are inherently related. A path-analytic approach is proposed to disentangle the interrelations.

Differential effects on PTSD symptom severity could be observed for threat to oneself (higher proximity of danger) as opposed to witnessing trauma (lower proximity to danger).

Further, PTSD symptom severity seems to mediate the relationship between dissociative re-sponding and depression symptoms.

In the second study, the physiological responding in women with and without PTSD was investigated using the cardiac defense paradigm. An acoustic noise of 0.5 s and 105 dB was used to elicit the cardiac defense reaction. The pattern of the cardiac defense consists of two accelerations and two decelerations of the heart rate. The first accelerative/ decelerative component reflects an attentional process and is associated with a parasympathetic with-drawal. The immediate increase of the heart rate accompanies an interruption of the ongoing perceptual processes as well as the physical movements. The following decrease in cardiac response is linked to heightened perceptual attention of the organism to threatening cues.

General Discussion 75

The second long-latency acceleration and deceleration of the heart rate prepares the body for active defense behavior such as flight or fight and seem to be associated with a stronger sym-pathetic dominance. The concept of the cardiac defense implies that it presents a physiologi-cal reaction to a high proximal threatening stimulus (Vila et al., 2007). The cardiac defense paradigm and the physiological background provide a good framework for noninvasively estimating the parasympathetic and sympathetic function as well as the regulation of the dy-namic physiological response in patients with PTSD. Whereas the Non-PTSD group showed a decrease after the first acceleration, the PTSD group showed elevated heart rate responses.

The elevation was associated with an ongoing withdrawal of the parasympathetic influence.

A pronounced first component was observed for those subjects with more severe PTSD. As in the first study, the traumatic event types were separated into the number of event types that were self-experienced and the number of witnessed traumatic event types. A less pronounced second accelerative component was associated with a higher exposure to self-experienced traumatic event types. Cumulative exposure to high proximal life-threat seems to reduce the preparation for active defense behavior such as flight or fight. The suppression of the second component provides evidence for a PTSD subtype that is associated with exposure to trauma such as rape or torture, where the victim is helplessly overwhelmed by an attacker and must adopt a shutdown defensive response. A systematic variation of the shutdown dissociation score on the heart rate change was not found. Further, the results indicated that the heart rate was influenced by the PTSD symptom severity. Additionally, the elevation in the heart rate was also found when the relationship was controlled for the cumulative trauma exposure, arguing for an augmented PTSD level for those that have increased heart rates. This is in contrast to previous studies that found that the dissociation plays a critical role in the physiol-ogy (Griffin et al., 1997; Medina et al., 2001; Lanius et al., 2002). Our results suggest that multiple exposure to life-threat followed by PTSD can on the one hand bring long lasting psychophysiological changes to the cardiac defense response and that on the other hand, sub-jects with greater autonomic responsitivity may respond with more intense symptoms.

Moreover with the dimensional approach the results confirm that there is significant variance within the group of PTSD that can be explained.

In the third study, the emotional processing of pictorial stimuli was assessed in women with and without PTSD. The rapid visual presentation paradigm was used to investi-gate the early emotional processing of unpleasant, pleasant and neutral photographs. PTSD patients showed deviant affective processing from the Non-PTSD group indicated by

differ-ences in valence and arousal ratings. PTSD patients showed exaggerated emotional respond-ing towards unpleasant pictures, whereas pleasant pictures were rated as less positive com-pared to the Non-PTSD group. The arousal ratings differed as well between PTSD and the Non-PTSD group, showing higher arousal ratings for unpleasant and neutral stimuli. Alto-gether, the PTSD and the Non-PTSD group rated the unpleasant pictures as more arousing compared to pleasant pictures. In line with the difference in arousal ratings, the heart rate data confirmed a higher physiological arousal in the unpleasant/ neutral block compared to the pleasant/ neutral block for both groups. As in the second study, the heart rate was posi-tively correlated to the PTSD symptom severity within the patient group. Moreover, the pic-tures that were presented in a rapid visual stream could evoke intrusive memories of different modalities, hence triggering the fear-network (Elbert et al., 2011). Event-related magnetic fields were recorded during streams of emotionally arousing stimuli (unpleasant or pleasant) that alternated with pictures from negligible affective content (neutral). Neural sources were estimated for each condition based on the L2 surface-minimum-norm. An early (mean from 60 to 110 ms) response differentiation between the high versus low arousal conditions were found in the PTSD group, but only a modulation of the early response between unpleasant and neutral stimuli in the Non-PTSD group. Relationships of shutdown dissociation, the de-gree of PTSD and depression symptom severity with the brain activities were explored. The cortical response in an early time window from 60 to 110 ms post stimulus onset correlated with the severity of depression symptoms for all picture categories. For shutdown dissocia-tion, positive correlations were found in the pleasant/ neutral block. In contrast, differential correlates were observed in the unpleasant/ neutral block, showing stronger correlates in the unpleasant versus neutral emotional processing. Additionally, the brain states that correlated with symptom severity of shutdown dissociation during the testing and PTSD were largely identical (67%) in unpleasant affective processing. The high convergence of the shutdown and PTSD severity on brain level for the processing of unpleasant stimuli was much lower for the neutral stimulation (26%). Further, the distribution of correlates of the unpleasant proc-essing show lower overlap with the depression symptoms and shutdown dissociation (31%) as well as depression and PTSD severity (33%). The PTSD symptom severity was associated with the minimum-norm estimate from 90 to 110 ms in the pleasant/ neutral block and the unpleasant/ neutral condition. Taken together, shutdown dissociation, PTSD and depression are all related to abnormal early visual processing of emotional stimuli. The neural network involved extends across a wide range of cerebral cortex.

General Discussion 77

The present thesis found that the dissociative responding is related to more severe PTSD and depressive symptoms. Compared to other studies, only a tendency of a relation-ship between trauma exposure and dissociative responding could be observed in the present thesis. The relative small sample sizes and therefore lower statistical power may have pre-vented detecting the moderate correlation between dissociation and cumulative trauma expo-sure (Carlson et al., 2012). On the brain level, a high convergence of the degree of shutdown and PTSD severity for the processing of unpleasant stimuli was observed. The high concor-dance confirms the close relationship between symptoms of PTSD and shutdown dissocia-tion. On the physiological basis, the findings supported the hypothesis of elevated heart rate reactivity for severe traumatized women with PTSD with different levels of dissociative re-sponding. Further, the stronger physiological reactivity is associated with a parasympathetic withdrawal.