Brain white matter structural connectivity of trauma and trauma-related dissociation disorders and symptoms

• Individuals with DID show reduced white matter integrity specifically for the pallidum, midbrain and pontocerebellar white matter compared to healthy controls (HCs), but increased white matter integrity in the right internal capsule and temporal white matter compared to PTSD. • White matter integrity was negatively correlated with traumatisation and dissociation symptoms. • These findings suggest significant structural brain differences in DID, linked to childhood traumatisation and dissociative symptoms. Experiencing repeated childhood traumatisation impacts brain structure and function in individuals with dissociative identity disorder (DID) and post-traumatic stress disorder (PTSD). Quantitative grey matter neuroimaging research has shown aberrant volumes in traumatised individuals, however studies examining white matter are sparse, particularly for DID. The present study aims to examine white matter alterations of people with trauma-related disorders. Sixty-five female participants were included in this study: 33 diagnosed with a trauma-related disorder, namely 17 with DID and 16 with PTSD, and 32 healthy control (HC) participants. All participants underwent diffusion tensor imaging (DTI) and completed dissociation and traumatisation self-report measures. White matter integrity was characterised using voxel-based analysis (VBA), with network lesion mapping used to identify the implicated grey matter end points of the VBA findings. Between-group VBA comparisons showed reduced fractional anisotropy (FA) for participants with DID compared to HCs in bilateral pallidum (implicating striatal projections to pre/post central gyri), midbrain, and pontocerebellar white matter. Compared to those with PTSD, DID subjects showed increased FA in the right internal capsule and right temporal areas (predominantly implicating the inferior longitudinal fasciculus). Across DID and PTSD subjects, FA values within the aforementioned findings negatively correlated with depersonalisation, psychoform and somatoform dissociation, and/or traumatisation scores. Our DTI findings indicate markedly differential white matter integrity in DID compared to PTSD and HCs. This provides valuable mechanistic insights regarding a role for aberrant white matter structural integrity in traumatised female individuals with DID.