Child maltreatment has a profound effect on the brain — even in kids who are resilient and don’t suffer from psychiatric disorders, according to two new studies, one of which found that brain activity in children raised in violent homes resembled that seen in soldiers exposed to combat.
For that study, published in Current Biology, researchers used functional MRI to image the brains of 43 London children as they looked at pictures of angry, sad or neutral faces. Twenty of the children, aged 11 to 13, were known to have been exposed to violence at home. They were compared with a matched group of 23 children from healthy families.
When looking at the faces in the scanner, children who had been exposed to violence showed increased activity in the amygdala and anterior insula in response to angry faces — a finding that is similar to that seen in soldiers with combat experience. These brain regions are thought to play a role in perceiving threat, and the heightened activity suggests hypervigilance to potential danger.
In any ongoing violent situation, being primed to perceive cues of threat — like angry faces or sudden, loud noises — can be beneficial, helping people elude harm. But while such brain changes may be adaptive in the short term, they can take a toll over time, increasing stress, anxiety and the risk of disorders like post-traumatic stress disorder (PTSD) and depression. Chronically elevated levels of stress hormones can also increase the risk of obesity, heart disease, stroke, diabetes and addictions.
MORE: Study: How Chronic Stress Can Lead to Depression
The children in the current study were healthy, and none suffered from mental health problems such as anxiety, depression or PTSD. But their brain activity suggested that they weren’t surviving their violent environments unscathed. “What we have shown is that exposure to family violence is associated with altered brain functioning in the absence of psychiatric symptoms and that these alterations may represent an underlying neural risk factor,” said lead author Eamon McCrory of University College London in a statement. “We suggest these changes may be adaptive for the child in the short term but may increase longer term risk.”
The second study this week, published in the Archives of Pediatric and Adolescent Medicine, examined the brains of 42 older youth, aged 12 to 17, some of whom were recruited from a separate, ongoing study on children who were identified at birth as being at high risk for parental neglect and abuse.
The teens were asked to report their experiences of maltreatment, including emotional abuse, emotional neglect, physical abuse, physical neglect and sexual abuse. As is typically found in research on the subject, the most common form of maltreatment was emotional neglect. Again, none of the children studied had psychiatric problems.
Researchers found, however, that the more types of trauma a child had experienced, the less gray matter (brain cell bodies) they had in certain key regions. Overall maltreatment was associated with reductions in volume in the prefrontal cortex (PFC), the brain region involved in deliberation, self-control and planning, and in the amygdala, which processes all types of emotions but is best known for its role in fear. Less gray matter as also seen in the striatum, a region involved in motivation, desire and pleasure.
MORE: The Case of the Texas Judge: When Does Spanking Cross the Line to Abuse?
The authors note that the PFC has been found in prior research to be one of the brain regions most vulnerable to stress — and of course, being abused or neglected is severely stressful for children.
MORE: Why Are So Many Foster Care Children Taking Antipsychotics?
Physical abuse was linked to smaller brain volume in the insula, an area that helps sense the body’s internal state, including whether experiences are likely to be painful or pleasant. It is also linked to empathy, which involves imagining the emotional states of others. The authors, led by Hilary Blumberg of the Yale Child Study, write:
We speculate that the association observed between physical abuse and the insula could contribute to alterations in perceptions of bodily ownership and personal agency, as well as dissociative symptoms observed in persons who have been exposed to childhood physical abuse.
Dissociative symptoms include feelings of emotional numbness or being “out of one’s body,” and are common in PTSD. Abused children often have particular difficulty feeling safe in their own skins and maintaining a sense of body integrity.
Some gender differences were also found in the teens’ brain responses to maltreatment. Girls showed greater reductions in the PFC, amygdala and insula — brain systems involved in controlling emotional responses. Boys saw greater changes in the caudate, a region linked with impulse control and pleasure. (Earlier research suggests that estrogen may protect the caudate and surrounding areas, which could explain why girls saw fewer changes in it.) The gender differences in brain changes may also help explain differences in men’s and women’s vulnerability to certain psychiatric disorders. For example, women are twice as likely as men to suffer depression, while men have a higher risk of substance misuse disorders.
MORE: The New Science Behind Children’s Temper Tantrums
Alternatively, there may be a bright side to the changes seen here. “Because the adolescents studied did not meet criteria for disorders in spite of adversity, it is also possible that the [gray matter] decreases reflect resiliency,” the authors write.
Although maltreatment dramatically increases risks for nearly all negative outcomes that researchers have studied, fortunately the majority of abused and neglected children escape the worst psychiatric consequences. Understanding what goes on in their brains could provide new insight into ways to heal those who do suffer the worst damage.
Maia Szalavitz is a health writer at TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.