Posttraumatic stress disorder symptom severity is associated with left hippocampal volume reduction: a meta-analytic...

Many studies have reported hippocampal volume reductions associated with posttraumatic stress disorder (PTSD), while others have not. Here we provide an updated meta-analysis of such reductions associated with PTSD and evaluate the association between symptom severity and hippocampal volume.

A total of 37 studies met the criteria for inclusion in the meta-analysis. Mean effect sizes (Hedges' g) and 95% confidence intervals (CI 95%) were computed for each study and then averaged to obtain an overall mean effect size across studies. Meta-regression was employed to examine the relationship between PTSD symptom severity and hippocampal volume.

Results showed that PTSD is associated with significant bilateral reduction of the hippocampus (left hippocampus effect size=-0.400, p<0.001, 5.24% reduction; right hippocampus effect size=-0.462, p<0.001, 5.23% reduction). Symptom severity, as measured by the Clinician-Administered PTSD Scale (CAPS), was significantly associated with decreased left, but not right, hippocampal volume.

PTSD was associated with significant bilateral volume reduction of the hippocampus. Increased symptom severity was significantly associated with reduced left hippocampal volume. This finding is consistent with the hypothesis that PTSD is more neurotoxic to the left hippocampus than to the right. However, whether the association between PTSD and lower hippocampal volume reflects a consequence of or a predisposition to PTSD remains unclear. More prospective studies are needed in this area.