Smaller Hippocampal Volume in Posttraumatic Stress Disorder: A Multisite ENIGMA-PGC Study: Subcortical Volumetry Results From Posttraumatic Stress Disorder Consortia.
Level 4 - case-series / case-control
Meta-analysis of cross-sectional case-control neuroimaging cohorts
PubMed 29217296 · doi:10.1016/j.biopsych.2017.09.006
What was done
The ENIGMA-PGC PTSD Working Group conducted a coordinated multi-site meta-analysis of structural neuroimaging data from 1,868 subjects (794 patients with current PTSD and trauma-exposed controls) across 16 cohorts. Brain MRI scans were processed using a standardized ENIGMA image-analysis and quality-control pipeline to measure volumes of eight subcortical regions: hippocampus, amygdala, nucleus accumbens, caudate, pallidum, putamen, thalamus, and lateral ventricles.
What was found
Individuals with current PTSD had significantly smaller hippocampal volumes compared with trauma-exposed controls (Cohen's d = -0.17, p = .00054). Amygdala volumes were also smaller (Cohen's d = -0.11, p = .025), but this did not survive Bonferroni correction across the eight subcortical regions (p < .0063). Numerical values for the remaining six subcortical regions were not reported in the abstract.
Why it matters
By harmonizing individual-level data across 16 international cohorts, this study clarifies inconsistencies in smaller imaging studies and confirms a robust, modest reduction in hippocampal volume associated with PTSD beyond the effect of trauma exposure alone.
Limits
The cross-sectional design prevents causal inference regarding whether smaller hippocampal volume is a pre-existing vulnerability or a neurotoxic consequence of trauma/PTSD. The observed effect size is small (d = -0.17). The abstract reports no data on potential confounding factors such as trauma type, illness duration, medication, or psychiatric comorbidities.
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