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Startseite > Forschung > Publikationen / Publications > Sebastian Siehl

Dr. Siehl


Siehl, S., Wicking, M., Pohlack, S. T., Winkelmann, T., …, & Nees, F. (2020). Structural white and gray matter differences in a large sample of patients with Posttraumatic Stress Disorder and a healthy and trauma-exposed control group: Diffusion tensor imaging and region-based morphometry. NeuroImage Clin., 28, 102424. doi:10.1016/j.nicl.2020.102424.

Differences in structural white and gray matter in survivors of traumatic experiences have been related to the development and maintenance of Posttraumatic Stress Disorder (PTSD). However, there are very few studies on diffusion tensor imaging and region based morphometry comparing patients with PTSD to two control groups, namely healthy individuals with or without trauma experience. It is also unknown if differences in white and gray matter are associated. In this cross-sectional study, we examined white- and gray matter differences between 44 patients with PTSD, 49 trauma control and 61 healthy control subjects. We compared the groups applying Tract-Based Spatial Statistics (TBSS) for a whole brain white matter analysis as well as region of interest analyses for white and gray matter. First, trauma control subjects in comparison to patients with PTSD and healthy control subjects showed significantly a) higher fractional anisotropy (FA) in the left corticospinal tract and inferior fronto-occipital fasciculus than patients with PTSD, b) higher FA in the left inferior fronto-occipital-, right inferior– and right superior longitudinal fasciculi, c) higher FA in the forceps minor and d) higher volume of the left and right anterior insulae. Second, we show significant correlations between the FA in the forceps minor and the gray matter volume in the left and right anterior insulae. Third, the mean FA value in the forceps minor correlated negatively with symptom severity of PTSD and depression as well as trait anxiety, whereas the gray matter volume in the left anterior insula correlated negatively with symptom severity in PTSD. Our findings underline the importance of brain structures critically involved in emotion regulation and salience mapping. While previous studies associated these processes primarily to functional and task-based differences in brain activity, we argue that morphometrical white and gray matter differences could serve as targets in neuroscientifically-informed prevention and treatment interventions for PTSD.

Siehl, S., Robjant, K., & Crombach, A. (2020). Systematic review and meta-analyses of the long-term efficacy of narrative exposure therapy for adults, children and perpetrators. Psychother. Res., pp. 1–16. PMID:33205713, doi:10.1080/10503307.2020.1847345.

Objective: Narrative Exposure Therapy (NET) is a short-term trauma-focused intervention originally developed for treating survivors of war and torture. The neurobiological theoretical foundations of NET would suggest that the approach should have long term beneficial effects. We tested this assumption and also provided an extensive overview of all NET studies for adults, for children (KIDNET), and for perpetrators (Forensic Offender Rehabilitation NET; FORNET). Method: Following a systematic literature review, we conducted meta-analyses with all studies that had control conditions, and with all Randomized Controlled Trials (RCTs). We assessed between-groups short- (< 6 months) and long-term (≥ 6 months) effect sizes for symptoms of posttraumatic stress disorder (PTSD) and depression. Results: In a total of 56 studies from 30 countries comparing 1370 participants treated with NET to 1055 controls, we found large between group effect sizes regarding the reduction of PTSD symptoms in favor of NET. Analyses of RCTs with active controls yielded small to medium effect sizes in the short-term, and large effect sizes in the long-term. Conclusions: NET, KIDNET, and FORNET yield beneficial and sustainable treatment results for severely traumatized individuals living in adverse circumstances. Studies in highly developed health care systems comparing NET with other evidence-based trauma-focused interventions are needed.

Wu, Y., Hall, A. S. M., Siehl, S., Grafman, J., & Krueger, F. (2020). Neural Signatures of Gender Differences in Interpersonal Trust. Front. Hum. Neurosci., 14, 225. PMID:32612518, doi:10.3389/fnhum.2020.00225.

Trust plays a critical role in nearly every aspect of social life. Parental investment theory and social role theory predict that women trust less than men due to a higher sensitivity to risk and betrayal, while men trust more than women to maximize resources and to signal their willingness to lose something. However, the underlying neuropsychological underpinnings for this gender difference are still obscure. In this study, we used functional magnetic resonance imaging (fMRI) to investigate the neural signatures of gender differences in trust by simultaneously scanning 11 male and 11 female same-gender, fixed dyads who played a multi-round binary trust game with varying levels of payoff (low/moderate/high) as an indicator of social risk. Our results showed that men trusted more than women and payoff level moderated the effect of gender on trust. While men trusted the same at all payoff levels, women trusted less with higher payoff levels. This pattern was supported by our neuroimaging finding: men showed a higher activation in the left inferior frontal gyrus (ventrolateral prefrontal cortex) and right precuneus than women, indicating that men exert more effort to inhibit the information of payoff levels and to use self-referencing to infer the strategies of partners with the goal of maximizing profit. Furthermore, men showed equivalent activation in the subgenual anterior cingulate cortex across payoff levels, whereas women showed a decreased activation with increasing payoff level - indicating decreased group bonding with higher risk in women. In conclusion, our results imply that women are more sensitive to social risk while trusting, which has implications for financial interactions, interpersonal relationships, and social involvement.


Crombach, A., & Siehl, S. (2018). Impact and cultural acceptance of the Narrative Exposure Therapy in the aftermath of a natural disaster in Burundi. BMC Psychiatry, 18(1), 233. PMID:30021559, doi:10.1186/s12888-018-1799-3.

BACKGROUND In the aftermath of natural disasters, affected populations are at risk of suffering from trauma-related mental health disorders such as posttraumatic stress disorder (PTSD) or depression. Particularly in poor post-conflict regions, these mental disorders have the potential to impair the ability of individuals to move on with their lives. We aimed to evaluate the feasibility, cultural acceptance, and effect of a trauma-focused psychotherapy, Narrative Exposure Therapy (NET), in the aftermath of a flood disaster in Burundi. METHODS Fifty-one individuals who were living in emergency camps overseen by the Burundian Red Cross in the aftermath of a flood disaster, and who had lost homes and close relatives, were invited to participate in semi-structured diagnostic interviews. Trained Burundian psychology students conducted these interviews, and six sessions of NET were offered to the 15 individuals most affected by trauma-related symptoms. An additional group of psychology students, blind to the treatment conditions, conducted three and 9 months follow-ups with them including also 25 participants who had reported significant but less severe trauma-related symptoms, assessing mental health symptoms, acceptance of NET, stigmatization due to trauma symptoms, and participants' economic well-being. RESULTS Between baseline and 9-months post-intervention assessment, symptoms of PTSD (Hedges' g = 3.44) and depression (Hedges' g = 1.88) improved significantly within participants who received NET and within those who received no treatment (Hedges' gPTSD = 2.55; Hedges' gdepression = 0.72). Furthermore, those who received NET felt less stigmatized by their participation in the intervention than by the trauma-related mental health symptoms they experienced. Overall, participants reported that they would be willing to forego as much as 1 month's worth of income in exchange for receiving trauma-focused interventions in the months following the disaster. CONCLUSIONS Individuals severely affected by trauma-related mental health symptoms might benefit significantly from NET in the aftermath of natural disasters, while less affected individuals seem to recover spontaneously. Despite significant challenges conducting NET in emergency camps in the aftermath of natural disaster in a post-conflict country, such interventions are feasible, appreciated and might have long-lasting impacts on the lives of survivors if conducted with due respect to participants' privacy. TRIAL REGISTRATION UKCR2014 , the 19.06.2014, retrospectively registered.

Siehl, S., King, J. A., Burgess, N., Flor, H., & Nees, F. (2018). Structural white matter changes in adults and children with posttraumatic stress disorder: A systematic review and meta-analysis. NeuroImage Clin., 19(February), 581–598. PMID:29984166, doi:10.1016/j.nicl.2018.05.013.

White matter plasticity occurs throughout life due to learning and can be a protective factor against as well as a vulnerability factor for the development of mental disorders. In this systematic review we summarize findings on structural white matter changes in children and adults with posttraumatic stress disorder (PTSD) and relate them to theoretical accounts of the pathophysiology of PTSD with a focus on the disturbed processing of contexts and associated problems in emotional and cognitive processing and PTSD symptomatology. We particularly examine studies reporting fractional anisotropy (FA) measured with diffusion tensor imaging (DTI). We further subdivided the studies in adult-onset PTSD with traumatic experience in adulthood, adult-onset PTSD with traumatic experience in childhood and children with PTSD. We included 30 studies comprising almost 1700 participants with 450 adults and 300 children suffering from PTSD. Our systematic review showed that for children with PTSD and adult-onset PTSD with childhood trauma, a decrease in FA in the corpus collosum, most prominently in the anterior and posterior midbody, the isthmus and splenium were reported. For adult-onset PTSD with traumatic experience in adulthood, changes in FA in the anterior and posterior part of the cingulum, the superior longitudinal fasciculus and frontal regions were found. Using GingerAle, we also performed a coordinate-based meta-analysis of 14 studies of adult-onset PTSD with traumatic experience in adulthood and did not find any significant clusters. Our results suggest that changes in white matter microstructure vary depending on traumatic experience and are associated with changes in brain circuits related to the processing of contexts. Finally, we present methodological considerations for future studies.