Mol Psychiatry: The hippocampus has been linked to non-recovery of PTSD

Numerous studies have examined the relationship between post-traumatic stress disorder (PTSD) and the hippocampus and amygdala, as both regions are implicated
in the pathogenesis and pathophysiology of the disorder.
The hippocampus is involved in providing contextual memory for emotionally related processes, while the amygdala regulates fear learning, elimination, and regulation
.
Previous literature generally reported that the hippocampus was smaller in PTSD patients, while the evidence for changes in amygdala volume was more equivocal, with no difference
in amygdala volume being smaller or larger in PTSD compared to controls.
A major unresolved question is whether the amount of these alterations reflects pre-traumatic vulnerability traits, is the result of the ongoing distress associated with the disorder, or a combination
of both.
The hippocampus and amygdala play a central role
in the pathogenesis of post-traumatic stress disorder (PTSD).

While volume changes in these two regions have been consistently observed in PTSD patients, it is unclear whether this reflects pre-traumatic vulnerability features or acquired consequences
of PTSD.

Yale University School of Medicine conducted a longitudinal group study
of adult civilian trauma survivors hospitalized in the emergency department (ED) of a general hospital.

100 eligible participants (mean age 32.
97±10.
97, n = 56 women) 1, 6 after admission to the emergency department and 14 months (also known as T1, T2 and T3).
Clinical interviews and structural MRI scans
were completed.
While all participants had a diagnosis of PTSD at T1, only n = 29 still had PTSD at T3 Diagnosed ("non-remission" group), n = 71 people did not ("remission "Group)
.

Hippocampal and amygdala subregion segmentation
.
Automatic segmentation of hippocampus and amygdala subregions, as generated by FreeSurfer 7.
1.
0 for one subject
.
Hippocampus subregion (a) and amygdala subregion (b).

Bayesian multilevel modeling analysis showed that the "non-remission" group had a smaller right hippocampus volume at T1 (P+ ~0.
014) and a larger left amygdala volume (P+ ~0.
870)
at T1 compared with the "remitted" group.

Subzone analysis further confirmed that the subregion and the right CA1 hippocampal subzone in the "non-remitted" group were smaller in size (P+ ~0.
021-0.
046).

No time-dependent volume changes (T1 to T2 to T3)
were observed between participants or groups.

Posterior distribution
of major effects in the 1-month post-traumatic (T1) group.

The results support the "vulnerability profile" hypothesis, suggesting that lower initial volume in specific subregions of the hippocampus is associated
with non-mitigation of PTSD.
The stable volume of all hippocampal and amygdala nucleon regions does not support the idea that corresponding, progressive, stress-related atrophy occurs during the
critical first year after traumatic exposure.

This work supports the role of
volumetric anomalies in specific hippocampal subregions as early vulnerability features associated with failure to recover from acute PTSD.
It further demonstrates that the volume of the hippocampal and amygdala subregions is stable during the first 14 months after trauma exposure, and therefore does not support the idea that
these regions develop progressive, stress-related atrophy in the critical first post-traumatic year.

Original source

Ben-Zion Z, Korem N, Spiller TR, et al.
Longitudinal volumetric evaluation of hippocampus and amygdala subregions in recent trauma survivors [published online ahead of print, 2022 Oct 24].
Mol Psychiatry.
2022; 10.
1038/s41380-022-01842-x.
doi:10.
1038/s41380-022-01842-x