Pieces of the puzzle
Dissociative identity disorder (DID) is a psychiatric disorder that, among others, is characterized by the presence of two or more distinct personality states that recurrently take control of a person's behaviour. DID was included in the DSM in 1980. Since then, an on-going debate regarding the etiology of the disorder is taking place between holders of the trauma- and fantasy model respectively. This thesis aims to explore the etiology of DID in a design that acknowledges both the trauma and fantasy model.
Based on psychological measures we showed that individuals with DID had the highest scores on trauma measures, followed by individuals with posttraumatic stress disorder (PTSD), and then controls (HC). On measures of fantasy proneness and suggestibility group differences were less pronounced, which is in contrast with the fantasy model’s hypothesis.
Using structural brain imaging we found that individuals with DID had a smaller hippocampal volume as compared with PTSD and HC. Furthermore, a negative relation was found between childhood traumatization and hippocampal shape and volume.
The first functional neuroimaging study showed that different personality states can be distinguished in DID during a working memory task, with the trauma-related personality state revealing worse task performance and limited activation of the prefrontal-parietal working memory network. The second study showed that when comparing individuals with DID with DID simulating controls differences in brain activation were found and actresses’ working memory performance was better. Overall, the thesis predominantly provides empirical support in favour of a trauma-related etiology for DID.