Experiences can reverse brain changes caused by early adversity
Photo: Beshr Abdulhadi. Creative Commons. 

We must find experiences that reverse brain changes caused by early adversity

By Seth Pollak and , | September 2019 

Brain development in children is influenced by good experiences, counteracting early trauma’s impacts, suggests neuroscience.

We need to identify and provide sustained experiences that can reverse or moderate the biological impacts of adversity on the brain development of children.

For example, children exposed to adversity may learn to cope with stress by becoming hypervigilant to signs of threat. These adaptations may help them manage some aspects of their early lives, but the biological imprints can leave them vulnerable to behavioral pathologies and make them overreact to less extreme situations later in life.

At the moment, we don’t know which interventions can alter children’s brain development for the better after early adversity has harmed them. However, we do know that the human brain is plastic, particularly when very young, and therefore mutable in ways that can not only harm but also benefit children in the long run.

Shaping brain development in children

We are also beginning to understand the nature of what shapes children’s brains. Research tells us that harm is typically caused by chronic experiences of extreme adversity.

Findings from experiments with rat pups suggest the potential for interventions that can tackle these harms. These studies showed that abusive parenting altered the genetics underlying the pups’ stress response system, so that the young rats had difficulty switching off their stress responses. However, when the same rats were moved and placed with responsive, caring mothers, that epigenetic change was reversed.

“The human brain is plastic and therefore mutable, in ways that can not only harm but also benefit children in the long run.”

Our next step must be to discover much more about how the human brain responds in positive ways to good experiences. This could help us identify interventions that can reverse the biological impacts of childhood adversity.

Neuroscience has already given us insights into the biological mechanisms that underpin the behavioral traits that often follow trauma, abuse, and deprivation in childhood.

How adversity affects brain development in children

The neurobiology of children subjected to physical abuse shares much in common with that of children who have been raised in extreme poverty or neglected. This fact suggests that the brain and stress systems learn and adapt in general ways when children find themselves in environments that subject them to high levels of stress.

Neuroscience also tells us that minor perturbations in experiences do not typically result in biological changes in the brain that have a cascading impact. Children’s brains can deal with a lot, and it takes something extreme or enduring to alter biological development.

For example, some people wonder what it is about child poverty that effects brain development. Is it living in a noisy environment? Is it lack of shelter or warmth, poor healthcare, stressed parents, or poor schooling? It likely wouldn’t be a problem if a child had to deal with just one of these components and everything else was OK. The biological needle is much more likely to shift when very young children are dealing with all of these factors at once, over a large period of their young lives.

It’s important here to recognise that infants don’t understand the physics of how the world works, or how social communication and language operate. They have to figure it all out, and this process can shape the brain that they will use throughout life. So a child’s brain will adapt to regulate and cope with an atypical environment that confronts it, even if that adaptation proves costly in the way the child relates to the rest of the world later on in life.

Hypervigilant response to threat

For example, children who have been physically harmed by their caregivers may become hypervigilant to signs of threat. This immediate response might be helpful around a parent who repeatedly becomes suddenly and violently aggressive. Such alertness, monitoring imminent change, may give children more time, prompting them, for example, to leave a room and hide to prevent further injury.

However, hypervigilance can become a problem later on at school, where such children can get into trouble and be viewed as aggressive. They may overreact when they perceive other children or teachers to be angry with them. Such children may mistakenly think that other people are angry with them when, in fact, they are upset with something or someone else. They may also misread upset and other emotions as marks of impending aggression.

Genetic changes caused by experience

My own research points to aspects of biology that might be effective targets for intervention. For example, we found that children in chronically stressed environments showed a change in the genes that regulate how we process stress hormones. Their glucocorticoid receptor gene had a part that was turned off, so these children still had a normal stress response, but they had more difficulty shutting it down and calming themselves afterwards.

We have also done studies showing that children with very high levels of early exposure to stress struggle to update their thinking and behaviors when their environment changes.

“An intervention need not be a traditional form of psychotherapy, but could build on how the brain responds to change.”

In one study, children had to learn to pair pictures of different ordinary objects (like chairs or bottles) with rewards and punishments such as gaining or losing points. Children quickly learned which objects to choose in the game to earn the most points. But when we changed which objects were rewarded, we observed something important. Most children quickly updated their choices and started selecting the objects that were now rewarded, abandoning their previous choices. But children from high-stress backgrounds continued to stick with the options that they first learned, even though doing so was no longer adaptive.

This type of study may give us some neurological explanations underpinning why children from abusive home environments might continue to employ strategies that helped them navigate their atypical home environments even when they are no longer living with an abusive caregiver.

Distinguishing childhood from adult stress impacts

In another study, we measured the life circumstances of children who experienced extremely high levels of early life stress and those with typical levels of stress. We then followed the children until early adulthood. They returned to our lab as young adults, where we studied their brain activation and behavior as they made decisions.

This approach overcame a huge scientific problem concerning studies that ask adults to report their childhood experiences retrospectively. With these studies, it is often difficult to determine whether behavioral problems associated with stress reflect early childhood experiences, or current levels of stress. That’s because people with extremely stressful childhood circumstances often have chronically stressful lives.

In our study, early life stress was assessed prospectively, when the participants were children, thereby avoiding the potential biases associated with adult recall. Our study suggests that childhood stress exposure, more than current adult stress, accounts for brain differences in decision-making. It revealed that adults who experienced very high, chronic levels of stress exposure in their early childhoods had difficulty attending to and using signs of punishments and losses.

Stress leading to poor decision-making

Our really startling finding is that decreased brain responses to cues warning of negative outcomes were associated only with childhood stress exposure, not with current levels of stress in the participants’ adult lives.

Interestingly, these brain responses were also related to how often individual participants engaged in risky behaviors in their everyday lives. So this experiment uncovered a potential neurological explanation about how high stress in early childhood creates risk for a wide range of behavioral problems: altered brain activation seems to lead to poor judgment and decision-making.

Challenge for research and policy

It has become even clearer from my own research and that of colleagues that we need to do our best for children when they are young, because the impact of what happens in those years can be profound and long-lasting.

For older children who have had prolonged stressful lives, interventions really have to derive from the science of learning. Given what we know from neuroscience, an intervention need not be a traditional form of psychotherapy but could build upon one of the many aspects of how the brain responds to change. Researchers now must identify how to harness knowledge about the science of learning and translate these ideas into policies and practices that can improve the well-being of children who have been exposed to negative learning experiences.


 Plate RC, Bloomberg Z, Bolt DM, Bechner AM, Roeber BJ& Pollak SD (2019), Abused children experience high anger exposure, Frontiers in Psychology

 Birna RM, Roeberb BJ & Pollak SD (2017), Early childhood stress exposure, reward pathways, and adult decision making, PNAS, 114.51

 Harms MB, Shannon Bowen KE, Hanson JL & Pollak SD (2018), Instrumental learning and cognitive flexibility processes are impaired in children exposed to early life stress, Developmental Science, 21

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