Underlying Hippocampal Mechanism of Posttraumatic Stress Disorder Treatment Outcome: Evidence From Two Clinical Trials

Sigal Zilcha-Mano, Or Duek, Benjamin Suarez-Jimenez, Xi Zhu, Amit Lazarov, Liat Helpman, Nachshon Korem, Michal Malka, Ilan Harpaz-Rotem, Yuval Neria

Research output: Contribution to journalArticlepeer-review


Background: The hippocampus plays an important role in the pathophysiology of posttraumatic stress disorder (PTSD) and its prognosis. Accumulating findings suggest that individuals with larger pretreatment hippocampal volume are more likely to benefit from PTSD treatment, but the mechanism underlying this effect is unknown. We investigated whether further increase in hippocampal volume during treatment explains the better prognosis of individuals with greater pretreatment hippocampal volume. Methods: We collected structural magnetic resonance imagesfrom patients with PTSD before and after treatment. We examined whether larger hippocampal volume moderates the effect of increased hippocampal volume during treatment on symptom reduction. Given the relatively small sample sizes of treatment studies with pre- and posttreatment magnetic resonance imaging, we focused on effect sizes and sought to replicate findings in an external sample. We tested our hypothesis in study 1 (N = 38; prolonged exposure therapy) and then tested whether the results could be externally replicated in study 2 (N = 20; ketamine infusion followed by exposure therapy). Results: Findings from study 1 revealed that increased right hippocampal volume during treatment was associated with greater PTSD symptom reduction only in patients with greater pretreatment right hippocampal volume (p = .03; η2 = 0.13, a large effect). Findings were partially replicated in study 2 for depressive symptoms (p = .034; η2 = 0.25, a very large effect) and for PTSD symptoms (p = .15; η2 = 0.15, a large effect). Conclusions: Elucidating increased hippocampal volume as one of the neural mechanisms predictive of therapeutic outcome for individuals with larger pretreatment hippocampal volume may help identify clinical targets for this subgroup.

Original languageEnglish
Pages (from-to)867-874
Number of pages8
JournalBiological Psychiatry Global Open Science
Issue number4
StatePublished - Oct 2023

Bibliographical note

Publisher Copyright:
© 2023 The Authors


  • Hippocampal volume
  • Hippocampus
  • Ketamine
  • Neural mechanisms
  • PTSD
  • Prolonged exposure therapy

ASJC Scopus subject areas

  • Clinical Neurology
  • Psychiatry and Mental health
  • Biological Psychiatry
  • Psychiatric Mental Health


Dive into the research topics of 'Underlying Hippocampal Mechanism of Posttraumatic Stress Disorder Treatment Outcome: Evidence From Two Clinical Trials'. Together they form a unique fingerprint.

Cite this