Source: University College London

Summary: A recent study shows that, contrary to popular belief, human newborn’s brains aren’t substantially less developed than monkey species. It just appears that way since so much brain growth occurs after birth.

Humans have brains that are typically developed for similar primate species at birth. However, because human brains are so complex than other species, it is mistakenly believed that newborn humans are underdeveloped.

According to lead author Dr. Aida Gomez-Robles of UCL Anthropology, “This new work changes the overall understanding of the evolution of human brain development. Humans seem so much more helpless when they’re young compared to other primates, not because their brains are comparatively underdeveloped but because they still have much further to go.”

Measuring the difference between a species’ birth and adult brain sizes allows scientists to study how their brains evolve.

People appear less mature at birth than other monkey species because humans have smaller brains than other monkeys.

This new study, however, demonstrates that this metric is deceptive because human brain growth is broadly comparable to that of other primates, including chimpanzees, bonobos, gorillas, and orangutans, according to other assessments.

The study casts doubt on accepted theories about how the human brain develops over evolution.

Due to less physical control, it has been believed that humans are born with less developed brains than other animals.

In order for newborn’s heads to fit through their mothers’ birth canal, they had to further develop outside of the womb, which was assumed to be the outcome of an evolutionary compromise.

On the basis of this knowledge, scientists proposed that humans have more pliable brains in their early lives and are more susceptible to external stimuli as they mature, because humans emerged relatively underdeveloped.

It was believed that this early underdevelopment led to increased brain plasticity, which in turn promoted human intelligence.

The reason why human brains take longer to reach their maximum potential than those of other animals

It’s not because their brains are significantly underdeveloped at birth, researchers claim; it’s because their brains develop far more slowly.

Results make it less likely that humans’ superior brain plasticity is the result of being born less developed than other primates. The researchers noted that their findings do not discount the significance of brain plasticity in human evolution.

Scientists examined 140 distinct mammal species including primates, rodents, carnivores and related ancestors of hominins, to understand the human brain.

To comprehend how human brains evolved, researchers analysed the length of fatal gestation in current mammals. The proportion of newborn bodies and brains to those of adults, and the total size of newborn and adult brains

Researchers found that while the brain development of many animal species varies significantly at birth, monkeys’ brains are quite similar.

Both current monkeys and their hominin relatives do not have considerably lower developmental stages at birth than humans.

In the US, the National Institutes of Health and the National Science Foundation funded the study.

Source: Garvan Institute of Medical Research

Summary: Chronic stress can suppress the body’s natural satiety signals, increasing appetite and boosting desires for sweets.

Chronic stress suppresses the brain’s normal satiety-inducing reaction, resulting in continuous reward signals that encourage the consumption of more appetizing food.

This happens in an area of the brain known as the lateral habenula, which normally blocks these reward impulses when it is active.

Professor Herzog, the study’s principal author and visiting scientist at the Garvan Institute, comments, “Our findings reveal stress can override a natural brain response that diminishes the pleasure gained from eating — meaning the brain is continuously rewarded to eat.”

“We showed that chronic stress, combined with a high-calorie diet, can drive more and more food intake as well as a preference for sweet, highly palatable food, thereby promoting weight gain and obesity. This research highlights how crucial a healthy diet is during times of stress.

From mental stress to weight gain:

While some people choose to eat less than usual during stressful times, most people choose calorie-dense, high-sugar, and fatty foods.

To understand what drives these eating behaviours, the team examined how different brain regions responded to long-term stress under varying diets in mouse models.

“We discovered that an area known as the lateral habenula, which is normally involved in switching off the brain’s reward response, was active in mice on a short-term, high-fat diet to protect the animal from overeating. However, when mice are chronically stressed, this part of the brain remains silent — allowing the reward signals to stay active and encourage feeding for pleasure, no longer responding to satiety regulatory signals,” explains first author Dr Kenny Chi Kin Ip from the Garvan Institute.

“We found that stressed mice on a high-fat diet gained twice as much weight as mice on the same diet that were not stressed.”

Researchers discovered that the primary cause of weight gain was the chemical NPY, which the brain normally produces in response to stress.

Stress mice on a high-fat diet consumed fewer comfort foods and gained less weight when the researchers prevented NPY from activating brain cells in the lateral habenula.

Next, in a “sucralose preference test,” the mice were offered the choice of drinking water or water that had been artificially sweetened by the investigators.

“Stressed mice on a high-fat diet consumed three times more sucralose than mice that were on a high-fat diet alone, suggesting that stress not only activates more reward when eating but specifically drives a craving for sweet, palatable food,” says Professor Herzog.

“Crucially, we did not see this preference for sweetened water in stressed mice that were on a regular diet.”

Chronic Stress outweighs a balanced, healthy energy level.

“In stressful situations it’s easy to use a lot of energy and the feeling of reward can calm you down — this is when a boost of energy through food is useful. But when experienced over long periods of time, stress appears to change the equation, driving eating that is bad for the body long term,” says Professor Herzog.

Stress is a major regulator of eating habits that can override the brain’s natural ability to balance energy needs, according to the study.

“This research emphasises just how much stress can compromise a healthy energy metabolism,” says Professor Herzog. “It’s a reminder to avoid a stressful lifestyle, and crucially — if you are dealing with long-term stress — try to eat a healthy diet and lock away the junk food.”

Source: American Psychological Association

Summary: Pregnant women who experience extreme stress, anxiety, or depression may put their unborn children at greater risk of developing mental health problems and behavioral problems as children and teenagers.

Tung and associates examined information from 55 studies, including almost 45,000 people in total. Each study assessed the psychological distress that expectant mothers experienced, such as stress, depression, or anxiety, and then examined the “externalizing behaviors”—outwardly directed mental health symptoms like aggression or attention deficit hyperactivity disorder—that their offspring exhibited.

According to parents, children born to pregnant women with higher levels of stress were more likely to behave aggressively.

Research has long suggested a link between pregnant women’s mental health and their child’s externalizing tendencies. However, in many previous studies, the effects of stress, anxiety, or depression during pregnancy have not been separated from the consequences of parents’ psychological distress after childbirth.

The only studies that the researchers included in this analysis assessed mothers’ psychological discomfort both during and after pregnancy. They discovered that psychological anguish during pregnancy, in particular, raised the chance of externalizing disorders in children, even after adjusting for postnatal psychological distress.

Whichever youngsters were involved—boys or girls—the effect was the same. It also remained true for kids in middle childhood (ages 6–12), adolescence (ages 13–18), and early childhood (ages 2–5), with the biggest influence occurring in the former.

The results corroborate notions that stress hormone exposure during pregnancy may impact a developing child’s brain.

According to Tung, future studies should concentrate on broadening their scope in order to comprehend the cultural and socioeconomic factors that influence perinatal stress and to create successful therapies.

“Most existing research has focused on white, middle-class, and higher-educated samples. But experiences of racism, economic disparities, and a lack of health care access are known contributors to stress during pregnancy. Understanding how psychological distress during pregnancy impacts underrepresented families is key to developing equitable public health policies and interventions,” she said.

She and her colleagues are now conducting two studies focused on understanding the types of support and resources that promote resilience and recovery from stress during pregnancy, particularly for families facing health inequities. The goal is to inform culturally inclusive preventive interventions during pregnancy to help support early mental health resilience and well-being for parents and their children.