Stress during pregnancy affects children's behavior into adulthood

Stress is a physiological and psychological response to situations perceived as threatening. It originates in the brain and triggers the release of hormones such as adrenaline and cortisol, which prepare the body to react: they increase heart rate, blood pressure, and the amount of available energy. This reaction is essential for survival in situations of real danger, but when sustained for so long that there is no chance of recovery, it can have negative effects. on physical and mental healthAdrenaline triggers the immediate stress response, while cortisol is responsible for maintaining a prolonged state of alertness.

It has long been known that glucocorticoids, a family of hormones that includes cortisol, affect brain plasticity, which, in turn, influences our present and future behaviors. A research team from the University of Göttingen and the Center for Primatology in Germany, led by biologist Oliver Schülke, who specializes in the evolution of social relationships, has analyzed how stress experienced during pregnancy affects brain development in offspring and what medium- and long-term repercussions this has. They analyzed this in Assam macaques, primates found mainly in Southeast Asia.

As described in the article they have published in Proceedings of the Royal Society B, Mothers' glucocorticoid levels during pregnancy alter the brain structure of their fetal offspring, affecting their behavior into adulthood. Given the enormous similarities in development between these primates and humans, the results obtained are largely applicable to humans and emphasize the importance of creating a stable and nurturing environment during pregnancy, benefiting not only mothers but also their children.

Harmful effects of cortisol

Chronic stress has a profound impact on the hypothalamic-pituitary-adrenal axis, the neuroendocrine system responsible for regulating the body's response to stressful situations. When a person experiences prolonged stress, the hypothalamus constantly activates the pituitary gland, which in turn stimulates the adrenal glands to release cortisol. This mechanism, which under normal conditions is adaptive and temporary, when sustained over time causes an overload of the system and alters the regulation of various bodily functions, such as metabolism, immune response, and brain neuroplasticity.

To see how stress experienced during pregnancy affects offspring, Schülke and her colleagues spent nine years following a group of Assam macaques, periodically collecting their feces to quantify the presence of glucocorticoids, such as cortisol, and assess their stress levels. They also collected data on various environmental factors known to promote chronic stress, such as food shortages and temperature fluctuations, and on social interactions, which, when adverse or conflictual, can also generate prolonged stress. Finally, they correlated all of this data with various physiological and behavioral parameters of the offspring.

The results obtained clearly indicate that the prolonged stress experienced by pregnant mothers, especially, but not limited to, adverse and conflictive social situations, negatively affects various physiological aspects of their offspring, including growth during childhood and the functioning of the immune system and the composition of the gut microbiome. It also affects brain plasticity and the functionality of the hypothalamic-pituitary-adrenal axis, resulting in alterations in their habitual behavior and in response to stressful situations. This altered behavior, in turn, favors adverse and conflictive social situations, which tends to perpetuate these effects.

In humans, this situation can lead to emotional hyperarousal and irritability, difficulty concentrating, and problems with decision-making. It can also affect memory and learning ability and increases the likelihood of suffering from mood disorders such as depression and anxiety. It also increases the risk of cardiovascular disease, metabolic disorders such as type 2 diabetes, and other mental health problems. As the authors note at the end of the paper, these results suggest that even moderate variation in maternal glucocorticoids may be associated with variations in offspring. [...] Moderate stressors such as temporary food shortages and ambient temperatures outside the adult comfort zone can lead to transgenerational effects.