Sofia is in the park with her five-year-old daughter. She has her phone in one hand and is rummaging through her bag with the other for work papers. She’s tense. Her voice sounds halting when she answers her little girl, who runs to show her something in the sandbox. “I can’t right now, Emma,” she says without looking at her. Minutes later, the girl gets frustrated, throws down the shovel, and starts screaming. The tension between them spreads, creating a silent loop.

Scenes like this are more common than they seem. And they’re not exactly harmless. Numerous studies highlight that in these early years, the infant brain is highly susceptible to biological, psychological, and environmental factors. And among them, parental stress has emerged as a significant risk to proper early development.

The window of vulnerability

During the first two years of life, the brain grows and organizes itself at an unprecedented rate through processes such as synaptogenesis (the formation of new neuronal connections), myelination (the coating of nerve cell axons to accelerate impulse transmission), and the formation of functional neural networks. This is why this stage is considered a crucial period for establishing cognitive and behavioral abilities that will last throughout life.

Consequently, environmental conditions—such as chronic stress at home—can alter brain maturation trajectories. In fact, several studies have shown that infants born to mothers with high levels of physiological stress exhibit brain activity patterns that are atypical for their age.

In particular, chronic maternal stress (measured by cortisol levels in hair) is associated with slower brain maturation. This manifests on the electroencephalogram as reduced activity in high-frequency ranges (alpha and gamma waves) and increased activity in low-frequency ranges (theta waves). These alterations can lead to lasting cognitive consequences.

In fact, without an adult to provide containment and support, acute stress (for example, that resulting from extreme poverty, abuse, or severe maternal depression) can weaken the architecture of the developing brain , with long-term negative consequences for learning and other cognitive functions.

It is not surprising, then, that children’s cognitive performance suffers when the home environment is highly stressful. Preschool children with greater difficulties in their executive functions (such as working memory, impulse control, or cognitive flexibility) tend to have elevated cortisol levels , as do their parents.

In this vicious cycle, the stress of the caregivers increases that of the children, which in turn can impair their ability to cognitive self-regulate.

Emotional impact

Parental stress doesn’t just affect a child’s intellect; it also profoundly shapes their emotional and social world. Growing up in a high-stress home has been linked to all sorts of emotional and behavioral problems in children, such as aggression, anxiety, and depressive symptoms. Researchers have even observed that children of parents who report high stress levels during their first year of parenting are twice as likely to experience mental health problems by age three .

One reason is the deterioration of emotional interactions. Chronically stressed parents are often more irritable, less patient, and less sensitive to their children’s emotional cues. Attachment science tells us that when a parent is overwhelmed, it is more difficult for them to provide the sensitive and responsive care that a baby or toddler needs.

This can lead to an insecure attachment in the child towards their parents; that is, they do not feel completely safe or confident in the adult’s emotional availability. This has been closely linked to behavioral problems in the preschool years and poorer emotional adjustment.

It has also been shown that children can “catch” the emotional state of their caregivers. Constant tension in the face, voice, or abrupt actions of mom or dad act as a nonverbal message that the child internalizes, often generating emotional instability.

The power of resilience

It is clear that the cognitive and emotional dimensions of child development are intimately intertwined with the well-being of their caregivers. When parents feel overwhelmed, children sense it and reflect it in their development: this can be seen in neural connections that mature more slowly, in words that are slow to emerge, in tantrums that become frequent, or in fears that are difficult to soothe.

The good news is that this impact doesn’t have to be permanent. Research suggests that various factors can moderate or lessen the effects of parental stress. For example, having family and social support networks, receiving parenting help, or learning stress management techniques can help. A recent study revealed that family resilience—the family’s ability to adapt positively to adversity—significantly reduced the negative impact of maternal stress on child development.

Author Bios: María J. García-Rubio is Professor at the Faculty of Health Sciences of the International University of Valencia – Co-director of the VIU-NED Chair of Global Neuroscience and Social Change – Member of the Psychology and Quality of Life Research Group (PsiCal) and Alejandro Cano Villagrasa is a Coordinator of the Degree in Speech Therapy both at the International University of Valencia