How Does Brain Structure Predict PTSD Risk in Soldiers Before Deployment?

What you need to know

• The size and symmetry of a brain region called the hippocampus before deployment may help predict which soldiers are at higher risk for developing PTSD symptoms
• Having a larger right hippocampus appears protective against developing PTSD symptoms when exposed to combat stress
• Asymmetry between the right and left hippocampus matters - having a larger right than left hippocampus is linked to fewer PTSD symptoms during deployment

Understanding the Hippocampus

The hippocampus is a region of the brain that plays important roles in memory, learning, and processing emotions. Scientists have long observed that this structure tends to be smaller in people with PTSD. However, it’s been unclear whether a smaller hippocampus makes someone more vulnerable to developing PTSD, or if PTSD causes the hippocampus to shrink.

This study helped answer this question by measuring soldiers’ hippocampus size before they deployed to Iraq and then tracking their stress exposure and PTSD symptoms during deployment. This allowed researchers to see how pre-existing differences in brain structure related to later symptoms.

The Role of Right vs Left Hippocampus

An interesting finding was that the right and left sides of the hippocampus appeared to have different relationships with PTSD risk:

• Soldiers with a larger right hippocampus were less likely to develop PTSD symptoms when exposed to combat stress
• Surprisingly, having a larger left hippocampus was associated with more PTSD symptoms under stress
• The difference in size between right and left hippocampus mattered - having a notably larger right than left hippocampus appeared protective

This asymmetry finding fits with other research showing that right-left hippocampus differences may be important for mental health. Most healthy people naturally have a slightly larger right hippocampus, while various psychiatric conditions have been linked to having a larger left than right hippocampus.

Why This Matters for Treatment

These findings suggest several important implications for preventing and treating PTSD:

• Brain scans measuring hippocampus size and symmetry could potentially help identify service members who may be at higher risk for PTSD before deployment
• Interventions that promote hippocampal growth, particularly in the right hippocampus, may help protect against PTSD
• Activities that stimulate the hippocampus, such as certain types of memory and spatial learning tasks, could be beneficial as part of PTSD prevention or treatment

Looking at Both Sides of Risk

While this study found interesting links between hippocampus structure and PTSD risk, it’s important to note that:

• The overall PTSD symptom levels in the study were relatively low, though more than 25% of soldiers did report significant symptoms at some point
• Many other factors beyond brain structure influence PTSD risk
• The study only included a small number of female soldiers, so more research is needed to confirm these patterns apply equally across genders

Conclusions

• Pre-existing differences in hippocampus size and symmetry may influence vulnerability to developing PTSD symptoms under stress
• Having a larger right hippocampus appears protective, while right-left asymmetry may be particularly important
• This knowledge could help identify at-risk individuals and develop better prevention strategies
• More research is still needed to fully understand these relationships and develop targeted interventions