Posttraumatic stress disorder often manifests in vivid flashbacks and relentless thoughts of the incident. But we don’t know much about how trauma changes the brain – and if some people’s brains are more susceptible than others to PTSD to begin with.
Now, working with survivors of the Great East Japan Earthquake from 11 March 2011, neuroscientists have identified a brain region whose size seems to predict susceptibility to PTSD symptoms and another brain region that shrank in people with the highest number of symptoms. ScienceNOW reports.
Previous imaging studies have shown that the parts of the brain involved in memory, fear, and mood control in PTSD sufferers are smaller compared with the brains of people who have come through their trauma relatively unscathed. But were these differences always there or did they appear after the trauma?
The earthquake, according to study researcher Atsushi Sekiguchi at Tohoku University, is a rare opportunity to tease apart cause and effect. (The coastal region of Tohoku was one of the hardest hit by the tsunami.)
- The researchers already had a lot of brain imaging data for university students before the earthquake for other reasons.
- They recruited 42 of those earlier subjects for MRI scans 3 to 4 months after the quake.
- The participants also rated the frequency and intensity of their PTSD symptom: intrusive memories, avoiding people or places associated with the trauma, heightened startle response, and feelings of re-experiencing the event.
None of the subjects had full-blown PTSD at the time of the test; the highest score on the symptom scale was just below the cutoff for a PTSD diagnosis. But the MRI scans showed that even 3 months after the trauma, some of the students’ brains were already changing in a way that tallied with PTSD symptoms.
- Even before the quake, a brain region called the right ventral anterior cingulate cortex (pictured, top) – which helps process fear and anxiety – was smaller in subjects with higher scores than in subjects with fewer symptoms. This region is one of the ones smaller in PTSD sufferers. The reduced size is a vulnerability factor for the disorder.
- Another area, called the left orbitofrontal cortex (pictured, bottom), seemed to be affected by the trauma itself. Students who showed a decrease in volume of this area, compared with their earlier scans, had higher PTSD scores. This region – involved in eliminating fear-related memories – proved to be smaller in subjects with more intense symptoms. This structural change represents an acquired sign of PTSD.
Future strategies might include scanning people in advance who are expected to be involved in trauma, to spot those at risk for the disorder. Researchers might also develop neuroprotective drugs for specific brain areas.
The work was published in Molecular Psychiatry today.
Image from A. Sekiguch et al., Molecular Psychiatry