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HIPPOCAMPAL MORPOHLOGY AND CHILDHOOD TRAUMA
INTRODUCTION
Recent epidemiological and neurobiological research in trauma-related disorders has focused on the relationship between childhood and chronic trauma and dissociation. This has led to the recent nosological inclusion of a dissociative subtype of Posttraumatic Stress Disorder (PTSD) (Lanius et al. 2010) in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) (American Psychiatric Association 2013). The dissociative disorders category has also recently been placed next to the trauma- and stress-related disorders category “to indicate the close relationship between them”(Spiegel et al. 2013). However, neurobiological evidence for a close relationship between PTSD and dissociative disorders is sparse. Furthermore, to date, the link between neuroanatomical abnormalities and childhood traumatization and/ or dissociative symptoms in PTSD and dissociative disorders remains unclear.
A smaller hippocampal volume is the most consistently reported neuroanatomical finding in individuals with a history of childhood adversity, with or without psychiatric disorders (Andersen et al. 2008, Bremner et al. 2003, Dannlowski et al. 2012, Samplin et al. 2013, Stein et al. 1997, Thomaes et al. 2010). Relevant to our study, a meta-analysis of structural brain imaging studies in childhood-related PTSD has revealed significantly smaller hippocampal volume in adults, but not children, with PTSD compared with healthy controls (HC) (Woon, Hedges 2008). However, none of these PTSD studies has investigated hippocampal shape or the regional specificity of hippocampal volume reductions in this disorder. The relation between hippocampal morphology and childhood adversity also remains unknown. Furthermore, evidence relating hippocampal structural abnormality to the severity of dissociative symptoms in PTSD is mixed. While some PTSD studies have reported a negative correlation between global hippocampal volume and severity of dissociative symptoms (Bremner et al. 2003, Stein et al. 1997), others reported no significant association (Bremner et al. 1995, Nardo et al. 2013). Therefore, the relationship between hippocampal morphology, childhood maltreatment and dissociative symptoms in a sufficiently large sample of PTSD patients is still open to test.
So far, only few structural imaging studies have investigated hippocampal volume in dissociative disorders (Ehling, Nijenhuis & Krikke 2008, Irle et al. 2009, Stein et al. 1997, Tsai et al. 1999, Vermetten et al. 2006, Weniger et al.
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