March 05, 2007

Studies Show How Stress Damages Young Brains

Research in the past has suggested that people who are genetically or biologically predisposed to schizophrenia and other mental illnesses are more sensitive to stress in their family and broader social environment. (see research here, here and here - and social isolation also causes significant stress for children). This area of research on how environment affects genes is called epigenetics, and we've covered this topic in the past here.

This past week there have been two studies published that suggest how stress may damage the brains of young children.

The first study is based on new research from the Child Development Laboratory at the University of Maryland shows that shyness (also called "social anxiety" by psychologists) in children seems to be triggered when a stress-related gene in children interacts with being raised by stressed-out parents. In this study the research focused on how moderate levels of parental stress (i.e. work related, or interpersonal stress) impacted child development.

In the study (published in the February issue of Current Directions in Psychological Science), Nathan Fox, professor and director of the Child Development Laboratory, and his team found that kids who are consistently shy while growing up are particularly likely to be raised by stressed-out parents, and to possess a genetic variant associated with stress sensitivity.

This suggests that shyness is caused by interactions between genes and the environment, as opposed to either genes or the environment acting alone. "Moms who report being stressed are likely to act differently toward their child than moms who report little stress," said Fox. "A mom under stress transfers that stress to the child. However, each child reacts to that stress somewhat differently. The study found that genes play a role in this variability, such that those children who have a stress-sensitive variant of a serotonin-related gene are particularly likely to appear shy while growing up when they also are raised by mothers with high levels of stress.

"We don't understand how the environment directly affects the gene, but we know that the gene shows particularly strong relationships to behavior in certain environments." Dr. Fox suggested.

Like all genes, the particular serotonin-related gene examined in this study has 2 alleles (alleles are the different versions of the same gene - with slight differences), which can be long or short. The protein produced by the short form of the gene is known to predispose towards some forms of stress sensitivity.

Fox's research found that among children exposed to a mother's stress, it was only those who also inherited the short forms of the gene who showed consistently shy behavior.

"If you have two short alleles of this serotonin gene, but your mom is not stressed, you will be no more shy than your peers as a school age child," says Fox. "But we found that when stress enters the picture, the gene starts to show a strong relationship to the child's behavior," says Fox. "If you are raised in a stressful environment, and you inherit the short form of the gene, there is a higher likelihood that you will be fearful, anxious or depressed." Additional research suggests that shy people are also at a significantly higher risk for anxiety disorders, clinical depression and suicide if they experience high levels of stress later in life, however, research also suggests that psychological therapy can reduce this risk of anxiety, depression and suicide for people who are shy.

This research on social anxiety / shyness also ties into the latest theories on social epigenetics, parenting and children's mental health. Researchers are now recognizing that parenting approaches that are highly attuned to the child's state of mind, and which are sensitive to the child's fears and stresses, shows empathy towards the fears, and seeks to lower those anxieties by educating the child about positive responses to the fears - are parenting approaches that seem to result in the children with the lowest risk of mental illness. See these links for more information here and here.
For more information on how to reduce stress for babies and young children we recommend this document: "Its a Stressful Life: How to Reduce Stress for Babies" and related information from

In another new study out of Stanford University in California, research suggests that severe stress can damage even the brains of children who don't have a biological predisposition to shyness or mental illness, say researchers. The researchers at the Stanford University School of Medicine and Lucile Packard Children's Hospital in Palo Alto, California found that children with post-traumatic stress disorder and high levels of the stress hormone cortisol were likely to experience a decrease in the size of the hippocampus - a brain structure important in memory processing and emotion.

Although similar effects have been seen in animal studies, this is the first time the findings have been replicated in children. The researchers focused on kids in extreme situations to better understand how stress affects brain development.

"We're not talking about the stress of doing your homework or fighting with your dad," said Packard Children's child psychiatrist Victor Carrion, MD. "We're talking about traumatic stress. These kids feel like they're stuck in the middle of a street with a truck barreling down at them."

Carrion, assistant professor of child and adolescent psychiatry at the medical school and director of Stanford's early life stress research program, and his collaborators speculate that cognitive deficits arising from stress hormones interfere with psychiatric therapy and prolong symptoms.

The children in the study were suffering from post-traumatic stress disorder, or PTSD, as a result of undergoing physical, emotional or sexual abuse, witnessing violence or experiencing lasting separation and loss. This type of developmental trauma often impairs the child's ability to reach social, emotional and academic milestones.

"We'd really like to understand why some children are more resilient than others, and what the long-term effects of extreme stress are," said Carrion, who is the first author of the research, to be published in the March issue of Pediatrics. "We know, for example, that these children are at higher risk of developing depression and/or anxiety as adults."

One theory posits that everyone carries an ongoing stress burden that accumulates throughout life. Once a certain threshold is reached, either through one or two very traumatic events or through chronic, high levels of stress, adults and children can begin to exhibit PTSD symptoms such as re-experience (including flashbacks, intrusive thoughts or nightmares), avoidance and emotional numbing, and physiological hyperarousal (such as an elevated resting heart rate). These behavioral symptoms make PTSD difficult to differentiate from other conditions such as attention deficit/hyperactivity disorder.

Children predisposed by genetics or environment to be more anxious than their peers are also more likely to develop PTSD in response to emotional trauma, perhaps because their responses to other life experiences simply left them closer to that threshold than less-anxious children.

The researchers studied 15 children from ages 7 to 13 suffering from PTSD. They measured the volume of the hippocampus at the beginning and end of the 12- to 18-month study period. After correcting for gender and for physiological maturity, they found that kids with more severe PTSD symptoms and higher bedtime cortisol levels (another marker of stress) at the start of the study were more likely to have reductions in their hippocampal volumes at the end of the study than their less-affected, but still traumatized peers.

It is significant that the change in the hippocampal volume corresponds to both PTSD symptom severity and increased cortisol levels. Cortisol belongs to a class of human hormones known as glucocorticoids that have been shown to kill hippocampal cells in animals. In a vicious cycle, a reduction in hippocampal size can make it more difficult for a child to process and deal with traumatic events, which in turn may raise both stress and cortisol levels that cause even more damage.

"Although everyday levels of stress are necessary to stimulate normal brain development, excess levels can be harmful," said Carrion, likening the biological effects of increasing amounts of stress to an inverted U. "One common treatment for PTSD is to help a sufferer develop a narrative of the traumatic experience. But if the stress of the event is affecting areas of the brain responsible for processing information and incorporating it into a story, that treatment may not be as effective."

Carrion and his colleagues are now using an imaging technique known as functional MRI to visualize whether and how the children's brains differ when performing emotional and cognitive tasks.

"What we have now is basically a snapshot," said Carrion. "We can't yet say much about function. But we know that PTSD is chronic and pervasive. Hopefully with further research we can develop more effective, targeted interventions to help these kids."

The study was funded by the National Institutes of Health, the National Alliance for Research on Schizophrenia and Depression, the American Foundation for Suicide Prevention and the Aloha Foundation.

Other co-authors include professor of psychiatry Allan Reiss, MD, and former postdoctoral scholar Carl Weems, PhD, who is now an associate professor of psychology at the University of New Orleans.

Related Story: Stress may 'damage child brains' (BBC)

Additional Reading:

Broken Homes Linked to Increased Risk of Psychosis, Schizophrenia

Social Intelligence More Useful Than IQ? Important for Mental Health

Early Family Experience Can Eliminate the Effects of Genes, Minimize Risk of Mental Illness

Stress Harms Baby's Brain While in Womb

Stress, Dopamine and Unusual Experiences in Everyday Life

Trauma Link to Schizophrenia is Strengthened by New Research

Is It Psychological Or Biological?

Related Research Papers:

Current Directions in Psychological Science (the research paper cited in the first news story does not yet seem to be available online).

Stress Predicts Brain Changes in Children: A Pilot Longitudinal Study on Youth Stress, Posttraumatic Stress Disorder, and the Hippocampus

Ordinary variations in maternal caregiving influence human infants' stress reactivity

Early family environment, current adversity, the serotonin transporter promoter polymorphism, and depressive symptomatology


It would be helpful to have a method of early screening and identification of very young children who would be vulnerable to normal stress, since children with a genetic predisposition to vulnerability may be harmed even by stressors that would be deemed beneficial to other kids. Over-protecting all kids from the normal stress would be developmentally inappropriate and even harmful to those kids who are not genetically vulnerable.

A certain amount of stress and hardship in our childhoods is what causes most of us to grow up to be successful adults. Without it, we may all grow up to have personality disorders and be unable to cope with normal adult life. But this same level of stress and hardship is what some vulnerable children may need to be protected against. And for the stressors that we can't shield them against - like a beloved pet dying (not to mention a grandparent, parent or sibling, or being involved in a car crash, tornado, etc) we need to know that these especially vulnerable children need to have more extensive mental health services available to them... and therefore, our government, insurance, whatever... needs to pay - the same as it would pay for services for any other developmental disability.

Perhaps all children need to be screened for neurological "soft signs", or if better diagnostic tests were created. It is my opinion that these vulnerable children can get "PTSD" from "minor" situations and stresses which "neurotypical" kids would just shrug off.

Posted by: Naomi at March 5, 2007 12:10 PM


Interesting points - certainly it seems like people with any family history of mental illness (that is, most of our visitors) might benefit from the idea of the early diagnostic testing you suggest.

There are simple saliva-based cortisol and DHEA tests that would be a good indicator of stress that a child or baby is experiencing - which might be the best way to measure a child's stress. Here is an example:

Cortisol Stress Test

Also - for families with a history of mental illness - it seems like it might be valuable to educate parents and children on how to lower stress in their lives and homes - so as to minimize the impact on the potentially sensitive children. Also - it seems reasonable to suspect that "positive psychology" (in which children are taught to take a positive interpretation of events) would also be valuable. There is a lot of psychology research that indicates that how you interpret an event can dictate your emotions and stress levels. This approach to life seems to be helpful for everyone - so there is no downside to taking this approach to training children. We might not be able to protect children from all stress, indeed, as you suggest we probably don't want to protect kids from all negative events. But what we can do - and what is extremely helpful it seems - is that we teach them positive ways to interpret events so that stress is minimized. See the links below:

The Optimistic Child: How To Raise Your Children To Be Optimists

Learned Optimism - by Dr. Martin Seligman

Posted by: szadmin at March 5, 2007 12:49 PM

''A certain amount of stress and hardship in our childhoods is what causes most of us to grow up to be successful adults. Without it, we may all grow up to have personality disorders and be unable to cope with normal adult life''

Naomi,whilst agreeing that a certain amount of stress is needed to help build up healthy resilience i think you will find that PDs are not the result of too little stress in
In fact i would go as far as to say that PDs are often the result of the individual having too much stress in relation to their ability to
cope with such stress or the experience of the kind of traumatic stressors that children are not equipped to cope with.

I agree that there needs to be better
targetting of those children who have a lessened ability to cope with 'normal' levels of stress.

Thankfully things are much better with regards to children's mental health than they used to be and there is more help out there for both childen and parents.

Certainly i think children with mental health problems nowadays will better equipped
to face the challenges ahead in relation to the severity of their problems than previous generations.

Things are heading in the right direction even if the train may be travelling more slowly than we
would sometimes like.

Posted by: Tim at March 5, 2007 01:53 PM

Tim, I was referring to the "spoiled brat", self-indulgent, feeling of entitlement - personality - that I remember some of the wealthier, spoiled kids developing due to their parents trying to completely eliminate any real-world "stress" and consequences from their lives.

For some of us, the normal kind of stress is a good thing - it develops our character and made us better able to cope with being an adult than some of our peers who were over-protected.

On the other-hand, I honestly believe that some vulnerable children NEED what would appear to be "over-protection" for a non-vulnerable child.

Perhaps my view is extreme - but then, my child was one of the 1-in-10,000 or so kids born with the developmental disorder of childhood-onset SZA. Now an adult, she is one of the few who has beaten the odds and is doing fairly well. I know it is considered to be "rare" (I sometimes wonder), but I think about how vulnerable they are, and how "mental hospitals" are NOT made for children like these, and neither are our school system, nor anything else.

Shielding all kids from the normal stresses that these kids are vulnerable to would MAKE the other kids ummm... warped? And our society doesn't invest in the psychological counselling and testing that would identify these kids at an early age and provide the individual and family training to make a real difference in their lives.

Even for the ones whose onset is in the teen years - perhaps the stress of middle school and highschool is too much for them. Maybe if these kids could be identified, they could be in a more nurturing environment than a school with 1000+ other kids and a LOT of bullies.


Posted by: Naomi at March 5, 2007 05:44 PM

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Posted by: Bound at June 18, 2008 12:41 PM

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