“The aftermath of that trauma could be seen in their brain scans, whether or not the young adults had developed diagnosable disorders. Regardless of their mental health status, formerly maltreated youth showed reductions in volume of about 6% on average in two parts of the hippocampus, and 4% reductions in regions called the subiculum and presubiculum, compared with people who had not been abused.

That’s where this study begins to tie together loose ends seen in prior research. Previous data have suggested that the high levels of stress hormones associated with child maltreatment can damage the hippocampus, which may in turn affect people’s ability to cope with stress later in life. In other words, early stress makes the brain less resilient to the effects of later stress. “We suspect that [the reductions we saw are] a consequence of maltreatment and a risk factor for developing PTSD following exposure to further traumas,” the authors write.”