prenatal stress

Humans and others exposed to prenatal stress have high stress levels after birth

April 10, 2018

Science Daily/Dartmouth College

Vertebrate species, including humans, exposed to stress prenatally tend to have higher stress hormones after birth, according to a new study. While previous research has reported examples of maternal stress experience predicting offspring stress hormones in different species, this study is the first to empirically demonstrate the impact of prenatal stress on offspring stress hormone levels using data from all known studies across vertebrates.

 

Through a meta-analysis of 114 results from a total of 39 observational and experimental studies across 14 vertebrate species, including birds, snakes, sheep and humans, the study examines the impact of prenatal exposure to maternal stress on offspring. The researchers analyzed the role of the hypothalamic pituitary adrenal (HPA)-axis, the stress physiological system that is shared across all vertebrates, which ultimately, results in the production of stress hormones known as "glucocorticoids." The HPA-axis is the hormonal system responsible for mobilizing an animal's stress response. Offspring exposed prenatally to maternal stress were found to have more stress hormone levels (glucocorticoids) after birth. This could reflect a biological adaptation with an evolutionary history, as more stress hormones could increase an animal's chances for survival in a stressful environment.

 

In the present study, the researchers tested the strength of the effect of prenatal stress on offspring stress hormone levels across a range of characteristics. Remarkably, the effects of prenatal stress on offspring stress hormones were consistent across species, regardless of evolutionary relationships or factors, such as brain or body size. There were also no differences when considering offspring sex, age of the offspring at the time of assessment, or the timing of the stressor exposure prenatally or its severity.

 

Only two factors influenced the size of the effect. Experimental studies had a stronger effect than observational studies. In addition, studies that measured glucocorticoid recovery showed a greater association with prenatal stress than was observed at baseline or during peak glucocorticoid response.

 

"Animals, including humans, modify their stress hormones in response to their environment. Your stress response is set like a thermostat -- your body can amp up or down stress hormones in response to anticipated environmental conditions," explains lead author Zaneta Thayer, an assistant professor of anthropology at Dartmouth.

 

An animal's stress response tends to be activated by external factors, such as when its see a predator or whether food is availabile. Higher stress hormone levels among offspring may help extend survival but come at a cost and may affect other physiological systems, such as reproduction. In humans, the mere anticipation of stress or just thinking about prior experiences of discrimination or trauma can activate a stress response. Overactive stress hormones can lead to chronic health problems in humans, including anxiety, depression and cardiovascular disease.

 

One of the studies included in the meta-analysis looked at how maternal stress hormones in pregnant snow hares changed in relation to the abundance of their natural predators, lynxes, over a 10-year cycle. The research team found that in years where there were more lynxes, snow hare offspring had more stress hormones and anti-predator behaviors.

 

"Our stress response is meant to be adaptive to acute stress, such as being chased by predators. However, humans' stress response is often triggered by social evaluative threats and is not serving the adaptive purpose that it was designed for," added Thayer. "This research confirms what other scientists have long speculated that there are trends across species when it comes to linking prenatal stress and offspring hormonal stress responses."

 

Prior work co-authored by Thayer has explored early origins of humans' health disparities and the impacts of maternal stress during pregnancy on offspring's postnatal stress hormone levels.

https://www.sciencedaily.com/releases/2018/04/180410161135.htm

Prenatal stress changes brain connectivity in-utero

New findings from developmental cognitive neuroscience

March 26, 2018

Science Daily/Cognitive Neuroscience Society

The time babies spend in the womb is far from idle. The brain is changing more rapidly during this time than at any other time in development. It is an active time for the fetus to grow and explore, and of course connect to its mother. New evidence from in-utero fetal brain scans shows, for the first time, that this connection directly affects brain developme

 

"It has long been thought that the stress of a mother during her pregnancy may imprint on the brain of her developing child," says Moriah Thomason of Wayne State University who is presenting this new work at the 25th meeting for the Cognitive Neuroscience Society in Boston today. "Despite the clear importance of this time frame, we presently possess very little understanding of how functional macroscale neural networks build during this precious time in human life, or the relevance of this to future human health and development."

 

This prenatal work is part of a growing body of research to better understand how the human brain develops across its lifespan, from fetus to old age. "We are interested in how a human brain constructs over time to become the adult brain," says Nim Tottenham of Columbia University, whose work focuses on identifying sensitive periods of brain development from childhood into adolescence. She is chairing a session on new findings in brain development at the CNS meeting: "The talks aim to bridge across the very long brain development that gives rise to mature functioning."

 

Seeing the changing fetal brain

 

Research in newborns and older children to understand prenatal influences has been confounded by the postnatal environment, Thomason explains. But recent advancements in fetal imaging allowed her and her team to gain insight into a critical time period in brain development never previously accessible.

 

Using fetal resting-state fMRI, they examined functional connectivity in 47 human fetuses scanned between the 30th and 37th week of gestation. The researchers recruited the participating mothers from a low-resource and high-stress urban setting, with many reporting high-levels of depression, anxiety, worry, and stress.

 

They found that mothers reporting high stress had fetuses with a reduced efficiency in how their neural functional systems are organized. It is the first time, imaging has shown a direct influence of maternal stress on fetal brain development, independent of influences of the postnatal environment.

 

"The major thrill is that we have demonstrated what has long been theorized, but not yet observed in a human, which is that the stress of a mother during her pregnancy is reflected in connectional properties of her child's developing brain," Thomason says. The data suggest that the brain does not develop in a sequence from simplest systems (e.g., vision, motor) to more complex high-order systems, but perhaps instead first develops the areas that will be most critical in bridging across systems.

 

The researchers found that the cerebellum played a central role in the observed effects, suggesting it may be especially vulnerable to the effects of prenatal or early life stress. The cerebellum has the highest density of glucocorticoid receptors, which are involved in stress responses, than any other place in the brain. Thomason and her team plan to further investigate this as a possible mechanism for the stress responses they observed.

 

Although conducting in-utero brain scans are challenging -- first and foremost because of the always wriggling babies -- working with expectant mothers is quite rewarding, Thomason says. "A lot of our moms are interested in being part of this research, not because of concerns they have in their pregnancy," she says, "but because they appreciate the heightened vulnerability of budding human life, and this is an opportunity to help other women that may not have the same fortune in their circumstances."

 

Making connections into adulthood

 

Cognitive neuroscientists are especially interested in understanding sensitive periods of time when the environment has the largest influence on future brain functions. To identify such times, Tottenham of Columbia University has honed in on connections between the prefrontal cortex (PFC) and the amygdala.

 

"A majority of developmental change during childhood and adolescence are the changes in connections," she explains. "We have largely focused on the connections between the amygdala and prefrontal cortex because of the very large changes we have observed there across childhood and adolescence and their central role in emotional behaviors."

 

Studying awake children as young as 4-years old, Tottenham and colleagues identified developmental periods when the nature of the communication between the amygdala and the PFC operates differently than in an adult. The connections develop very slowly over childhood, with a dramatic shift toward the end of childhood when the transition to adolescence brings about more adult-like characteristics. Looking at coincidental environmental events in childhood, the researchers also found data to suggest that amygdala-medial PFC connections are highly impressionable to external forces.

 

"The human brain is designed to learn from the environment. This is thanks to the long period of infancy, childhood, and adolescence that humans enjoy," Tottenham says. "What has amazed me most about the developing brain is that it is not simply an immature version of the adult brain but instead is designed to collaborate with the expected caregiving ecology."

 

Indeed, says Thomason: "We must consider the developing brain in context, thinking about the role of the environment in shaping the brain. It is a topic that inspires us to promote healthy brain growth, to ask what it is that we do for children in the lifestyles, opportunities, and learning conditions we create for them."

https://www.sciencedaily.com/releases/2018/03/180326110123.htm

Now and Zen: Lower prenatal stress reduces risk of behavioral issues in kids

Study finds mothers who experience significant prenatal stress may be increasing their child's risk for behavioural issues

August 16, 2017

Science Daily/University of Ottawa

Expectant mothers may want to consider adopting today's trend towards stress management, in light of new research pointing to its ability to lower the risk of problematic behavior in their offspring. Researchers found that mothers who are exposed to high levels of stress during pregnancy have kids who are more than twice as likely to have chronic symptoms of hyperactivity and conduct disorder.

 

Parenting is a complicated journey full of questions, and when a beloved child begins to show signs of a behavioural disorder, a parent's challenges become even more difficult to navigate.

 

Expectant mothers may want to consider adopting today's trend towards stress management, in light of new research from the University of Ottawa pointing to its ability to lower the risk of problematic behaviour in their offspring.

 

Dr. Ian Colman, associate professor at the University of Ottawa's Faculty of Medicine, led a team of researchers in examining data from the Avon Longitudinal Study of Parents and Children. The team found that mothers who experience significant prenatal stress may be increasing their child's risk for behavioural issues.

 

"Mothers who are exposed to high levels of stress during pregnancy have kids who are more than twice as likely to have chronic symptoms of hyperactivity and conduct disorder," Dr. Colman said of the team's recently published findings.

 

"Hyperactivity is a symptom of ADHD, and about 10% of school-age children are affected by ADHD or conduct disorder," he said. "These disorders can lead to poor results in school and difficulties in their relationships with family and friends."

 

Behavioural disorders such as those seen by the researchers are characterized by aggressive or antisocial behaviour, high activity levels, and difficulty inhibiting behaviour. They are also associated with school failure, substance use/abuse, and criminal activity, according to the paper.

 

A mother's stress can alter brain development in the fetus, and it is believed these changes may be long-lasting or permanent, said Dr. Colman.

 

The team was unique in its approach: it studied the effects of specific stressors on participants, as opposed to gauging overall stress levels. Participants reported stressful events, such as problems at work, the illness of a relative, or an argument with a partner, family or friend. "Generally speaking, we found that the higher the stress, the higher the symptoms," Dr. Colman said. "We can't avoid most stressful events in our lives and since we can't always prevent them, the focus should be on helping mothers manage stress in order to give their children the best start in life."

https://www.sciencedaily.com/releases/2017/08/170816110136.htm

Prenatal stress could enhance protective mechanisms of babies

May 13, 2016

Science Daily/Universität Basel

Maternal stress and depression during pregnancy may activate certain protective mechanisms in babies. Psychologists from the University of Basel together with international colleagues report that certain epigenetic adaptations in newborns suggest this conclusion. Their results have been published in the journal Social Cognitive and Affective Neuroscience.

 

In their study, the researchers observed that increased concentrations of maternal stress hormones, depressive symptoms and general adversities during pregnancy were accompanied by epigenetic changes in the child. As a result of these changes the oxytocin receptor gene, which is important for social behavior and stress adaptations, is activated more easily. This mechanism could indicate that in these cases, the babies adapt to develop more resilience to cope with future challenges and adversities.

 

Switch reprogrammed

 

Whether a gene can be activated or not also depends on methyl groups that attach to the DNA and function as a switch. The researchers found that children from mothers with increased stress and depressive symptoms show a reduced methylation of the oxytocin receptor gene at birth. This results in the gene becoming more easily activated, which leads to a facilitated production of oxytocin receptors for oxytocin to react with and unfold its effects. Oxytocin not only has an important function in mother-child bonding and in induction of labor and lactation, it also influences social behavior.

 

For their study, the team of Prof. Gunther Meinlschmidt from the Faculty of Psychology at the University of Basel examined 100 mothers and their babies during and after pregnancy. They collected umbilical cord blood from 39 newborns and assessed the stress hormone cortisol in saliva samples of the mothers. In addition, the researchers evaluated stressful life events and mental health of the mothers via questionnaires. Since the data were only analyzed up to the newborn phase, no conclusions were drawn with regard to the long-term consequences that the epigenetic programming of oxytocin receptors might have for the children.

 

"Resilience research only at the beginning"

 

Researchers from the University of Basel, Ruhr University Bochum, Exeter University, McGill University Montreal, Ludwig Maximilian University of Munich, University of Trier, Zurich University of Applied Sciences and the Stress Center Trier were involved in this study funded by the Swiss National Science Foundation. Previous studies have shown, that adversities during pregnancy can increase the risk for mental disorders and physical diseases in the mother's offspring. However, science has so far dedicated much less attention to potential protective mechanisms of the child.

 

"Resilience research in this area is only at the beginning," explains Meinlschmidt. The observations made provide first evidence that an adverse environment during pregnancy could also activate protective mechanisms. "We need a comprehensive understanding of the psychological processes that allow humans to sustain long-term health even over generations despite adversities," says Meinlschmidt. Based on this knowledge, resilience processes could be promoted in order to try preventing the development of mental disorders and physical illnesses.

https://www.sciencedaily.com/releases/2016/05/160513084542.htm

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