Donders Institute for Brain, Cognition and Behaviour
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Thesis defense Clarisse Musanabaganwa (Donders Series 625)

11 September 2023

Promotors: Prof. dr. Benno Roozendaal and Prof. dr. Erno Hermans
Co-promotors: Prof. dr. Leon Mutesa (University of Rwanda, RW) and Dr. Stefan Jansen (University of Rwanda, RW)

Intergenerational and epigenetic effects of trauma and PTSD following exposure to the 1994 genocide against the Tutsi in Rwanda

The intergenerational trauma is a phenomenon in which the descendants of a person who has experienced a terrifying event show adverse emotional and behavioral reactions to the event that are similar to those of the person himself or herself. In this thesis, I investigated the intergenerational effects of trauma and post-traumatic stress disorder and associated biological mechanisms in a Rwandan post-genocide population. This was the main research question of the study and it was fostered based on the current alarming society issues on the burden of PTSD in the Rwandan population which is still extremely high almost three decades after the 1994 genocide against the Tutsi. The key findings from the thesis showed the differentially methylated regions (DMRs) in genocide-exposed vs. unexposed mothers and children. In utero genocide exposure was associated with methylation differences in three of the 24 maternal DMRs, with higher methylation in exposed offspring. The thesis also revealed a synthesized model that is more precise to capture the overall pooled estimate of PTSD prevalence. A meta-analysis approach was applied and a pooled prevalence of 25% for PTSD was observed. Besides, the pooled prevalence among the genocide survivors’ group was very high as expected (37%).

Moreover, this thesis shared efforts and lesson learnt from establishing community engagement (CE) for epigenomic and neurocognitive research in Rwanda. Most importantly, the CE enabled the development and validation of a memory task relying to other tested memory paradigms. The implementation includes trauma word lists related to the context of Rwanda and the Rwandan genocide, both in culture and language, and neutral word lists.

Lastly, this research thesis showed that household members from the new recruited study participants (i.e., mothers, first child, second child) from the case group had significantly higher PTSD symptom scores, and lower cortisol levels than those from the control group. Additionally, there were significant associations between cortisol levels and PTSD symptoms.