Witnessing their mother's acute and prolonged stress affects executive functioning in children

Psychosocial stress significantly impacts physical and mental health, particularly during childhood's vulnerable developmental period. Parental bonds play a crucial role, either protecting against or exacerbating stress experiences. This study investigates the impact of mothers' everyday stress on their children's executive functioning, focusing on the dual role parents play in shaping their children's stress resilience. Resilience is defined here as a measurable positive outcome in the face of stress. Stress is considered from environmental (stressors), psychological (subjective perceptions and emotional responses), and biological (physiological stress response) perspectives. Most research focuses on singular traumatic events, but this study examines the frequent impact of everyday social interaction stress. The researchers hypothesized that children's psychophysiological stress responses and executive functioning would be affected by observing their mothers undergoing experimental stress. Early experiences with attachment figures shape children's ability to interpret social cues and regulate emotions; empathy and physiological synchrony enhance maternal responsivity and strengthen the mother-child bond. However, strong empathic tendencies in children might lead to negative outcomes when consistently sharing their mother's negative emotions or stress. Empathic stress responses mirror first-hand stress, including cortisol release, increased heart rate, and decreased HF-HRV. Family bonds provide a context to investigate empathic stress and its potential maladaptive consequences. Previous research has shown stress transmission between family members, with affect spillover from parents to children. Physiological covariation between mothers and children has been observed during stressful situations, suggesting immediate pathways of stress transmission. While maternal attunement to children's stress has been studied, fewer studies explore how children physiologically resonate with stressed mothers. A previous study by the same research team demonstrated a causal link between maternal psychosocial stress and children's empathic stress responses. The current study uses the same mother-child dyads to investigate children's cognitive performance following observation of their mothers' stress exposure. Since frequent stress alters the stress system's basal activity and responsiveness, the researchers explored how prolonged stress perceptions in mothers and children might interact with children's acute stress responses. Cognitive development progresses rapidly during childhood, and early impairment of executive functions like cognitive flexibility and working memory can have lasting consequences. While adult studies show acute stress negatively affects these functions, research in children is scarce. Chronic stress studies link early life adversity to impaired cognitive flexibility and working memory. The prefrontal cortex (PFC), crucial for executive functioning, is highly sensitive to the neuroendocrine environment and shows structural changes after prolonged psychosocial stress. The study aimed to empirically link maternal stress (both acute and prolonged) to children's cognitive outcomes, given the central role of the mother-child bond for child development and resilience.

Existing literature highlights the detrimental effects of extreme or chronic psychosocial stress on the physical and mental health of children. Parental bonds can either buffer or amplify these effects. The concept of resilience is examined as an outcome, trait, or process. This study emphasizes resilience as a measurable outcome in response to stressful situations. The literature review extensively covers studies on empathic stress and its transmission within families, particularly focusing on physiological covariation between mothers and children in response to stressful events. Research on the effects of acute and chronic stress on executive functions, including cognitive flexibility and working memory, in both adults and children is reviewed. The literature emphasizes the impact of early life adversity and chronic stress on cognitive development and the sensitivity of the prefrontal cortex to stress. The study also references a previous study by the research team demonstrating a causal link between maternal psychosocial stress and children's empathic stress responses.

Seventy-six healthy mother-child dyads (31-45 years old mothers; 8-12 years old children) participated. Exclusion criteria included pregnancy, smoking, drug use, excessive alcohol consumption, BMI outside the 18.5-30 range, lack of German fluency, and pre-existing health conditions. Dyads were randomly assigned to an experimental (n=39) or control group (n=37). The study received ethics approval from Leipzig University. Testing involved a 2.5-hour session. Mothers and children were separated initially, and mothers completed either the Trier Social Stress Test (TSST; experimental group) or a stress-free reading task (control group). Children observed their mothers through a one-way mirror. Acute stress reactions were assessed through eight measurements each of subjective stress, heart rate, and salivary cortisol, from 20 minutes before to 70 minutes after the task. Children completed computerized cognitive tasks assessing cognitive flexibility (category-switching task) and working memory (n-back task). Questionnaires assessed mothers' and children's perceived stress (past month for mothers, past week for children), children's trait empathy, and relationship closeness. Acute stress reactivity was measured using the area under the curve (AUCi). Linear mixed models (LMMs) analyzed relationships between stress measures and cognitive performance. Models included children's age, sex, task characteristics, experimental group, children's stress reactivity (AUCi), maternal stress reactivity (AUCi), and an interaction term of child and maternal AUCi's. A three-way interaction of children's perceived stress, mothers' perceived stress, and experimental group was added to test for a modulating effect of recent everyday stress. Linear and quadratic models were employed to account for potential non-linear relationships between stress and cognitive performance. Moderation analyses used multiple linear regression to assess the role of children's empathy and relationship closeness in moderating the relationship between maternal and child prolonged stress.

The study found no significant group differences in children's cognitive performance between the TSST and control groups. However, individual-level analyses revealed several stress effects. For cognitive flexibility (category-switching task), children's acute cortisol response was associated with impaired accuracy. Importantly, maternal acute stress markers (subjective stress, heart rate, and cortisol) also predicted children's error rates. A quadratic relationship emerged, showing that both very low and very high maternal stress levels were associated with poorer performance. Children's own subjective stress showed a quadratic relationship with accuracy, with optimal accuracy around average stress reactivity. In contrast, the analysis of working memory (n-back task) revealed a significant positive relationship between maternal subjective stress and reaction time (faster response times with higher maternal subjective stress). For prolonged stress, maternal past-month stress showed a quadratic relationship with children's accuracy in the category-switching task, with optimal performance around 0.25 SD above average. A significant interaction effect emerged between maternal past-month stress and the experimental condition, indicating that lower maternal stress was associated with better accuracy in the control group but poorer accuracy in the TSST group. The reverse was true with higher levels of maternal prolonged stress. No evidence of a relationship between maternal and child prolonged stress was found. The hypothesized moderating roles of children's empathy and relationship closeness on the relationship between maternal and child prolonged stress were not supported.

The findings extend previous research by demonstrating that maternal stress, both acute and prolonged, significantly impacts children's executive functioning, specifically cognitive flexibility. While children's own stress response was linked to impaired performance, maternal stress proved a stronger predictor. The quadratic relationships highlight the complex interplay between stress and cognitive performance. The absence of significant interaction effects between maternal and child stress challenges the hypothesis of direct empathic stress resonance causing cognitive impairment, but rather points towards more indirect effects. The interaction between maternal past-month stress and the acute experimental condition might suggest adaptive mechanisms in children from high-stress environments. Children from chronically stressed environments might exhibit better resilience or emotional detachment. The lack of significant relationships between maternal and child prolonged stress might be attributed to the low levels of prolonged stress in the sample and limitations in the reliability and validity of the children's perceived stress scale. The study highlights the limitations of solely relying on children's stress response to explain the effects of maternal stress on children's cognitive performance. Future research should investigate other pathways such as altered parenting behavior.

This study demonstrates the significant impact of maternal stress on children's cognitive flexibility, particularly under acute and chronic conditions. The findings underscore the crucial role of the family environment in shaping children's cognitive development and stress resilience. The absence of a direct link between empathic stress resonance and cognitive impairment suggests other mediating factors require further investigation. Future research should use more diverse samples, incorporate more robust measures of chronic stress, and explore potential mediating factors such as altered parenting behavior or broader family stressors.

The sample size, primarily healthy German mother-child dyads, limits generalizability. The low levels of self-reported prolonged stress in the sample might have restricted the detection of nonlinear effects. The low reliability and validity of the child stress questionnaire compromised the results. The separation of mothers and children upon arrival might have reduced the occurrence of empathic stress. The unfamiliar environment and cognitive tasks may have influenced the children's stress response, making it difficult to isolate the effects of observing the mother's stress.