A Meta-Analysis of Hippocampal and Amygdala Volumes in Patients Diagnosed With Dissociative Identity Disorder

Abstract

Dissociative Identity Disorder (DID), an illness characterized by multiple personality states, has long been a controversial diagnosis within the psychiatric community. Demonstrating a neuroanatomical basis for the disorder may help to resolve the controversy. Current literature on the neuroanatomy associated with DID has focused on the hippocampus and amygdala and are inconclusive. This meta-analysis pools the results from n = 3 studies to compare the mean size of these two structures between DID patients, non-DID patients, and healthy controls. Patients diagnosed with both DID & PTSD were found to have smaller hippocampi bilaterally (p< .001) compared to healthy controls; no significant difference was seen in the amygdala. When comparing DID to PTSD patients, the left hippocampus was smaller (p< .001), with a trend for a smaller right hippocampus (p = .06). A comparison of the amygdala was not possible due to a lack of data. These findings suggest that a smaller hippocampus is seen in DID patients beyond what is seen for PTSD, provides neuroanatomical evidence for the memory impairment often seen in DID patients (i.e., amnesia experienced by the host and alters), and presents a potentially novel means to understand this disorder.

Dissociative Identity Disorder

“…Topics within the empirical articles included clinical features (28%), assessment (17%), etiology (17%), comorbidity (17%), cognitive features (8%), and treatment (7%). Among the 18 etiology articles, the biological approach was most common (Blihar et al, 2021;Campone, 2014;Dimitrova et al, 2023;Reinders et al, 2014;Schlumpf et al, 2014;Weniger et al, 2013), followed by the trauma model, although these articles often included biological components as well (Chalavi et al, 2015a(Chalavi et al, , 2015bDorahy et al, 2016;Krüger and Fletcher, 2017). Several articles directly compared the ability of multiple models of etiology to explain the results.…”

Understanding Dissociative Identity Disorder: A Literature Review

“…A meta-analysis showed that changes in amygdala and hippocampal volume in DID patients on magnetic resonance imaging (MRI) were similar to those with PTSD [27]. This is because the work of the limbic system affects human emotions which work more actively in DID patients [28].…”