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A recent study published in Psychoneuroendocrinology has uncovered a link between maternal stress, brain activity, and parenting behavior in new mothers. Researchers found that higher levels of cortisol were associated with more intrusive behaviors in mothers during interactions with their infants. Additionally, these elevated cortisol levels corresponded with reduced activity in several brain regions when the mothers heard their babies cry. This study is the first to explore the connections between maternal cortisol levels, brain response to infant distress, and parenting behavior in such detail.
Cortisol, a hormone produced by the body’s hypothalamic-pituitary-adrenal (HPA) axis, is central to the stress response. Elevated cortisol levels can affect a person’s ability to regulate emotions and respond to stressors, which are critical factors in parenting behavior. Previous studies had identified that higher basal cortisol levels were linked to less sensitive and more intrusive parenting, but much of this research lacked a clear understanding of the neural mechanisms involved.
By studying brain activity in response to infant crying, the researchers hoped to uncover how cortisol levels might alter maternal brain function, particularly in regions associated with emotional regulation and auditory processing. The motivation for this research was to bridge the gap between cortisol’s effects on the brain and how it might translate into observable caregiving behaviors.
“The goal of this research was to understand how the multiple biological systems that underpin parenting behavior interact,” said study author Andrew Erhart, the School Age Systems Specialist at the Colorado Department of Public Health and Environment, who conducted the research while a member of the University of Denver’s Family & Child Neuroscience Lab.
“We know that the transition to parenthood is a critical period where brain and body change to support the development of parenting behaviors. I am particularly interested in understanding how environmental influences like the postpartum environment and chronic stress moderate the biological changes in the transition to parenthood.”
“Understanding the biological systems themselves is a necessary first step. This is why we were particularly interested in examining the HPA axis as one biological component — it is a stress-responsive system thought to help motivate parenting behavior, and it is also particularly sensitive to environmental influence.”
The study involved 59 first-time mothers with infants aged 3 to 4 months. These mothers participated in both home and lab-based sessions designed to assess their cortisol levels, behavior during interactions with their infants, and brain responses to infant cries.
During the home visit, the researchers recorded 15-minute interactions between the mothers and their infants. The mothers were instructed to interact naturally without the use of toys, while their behavior was later coded for two parenting qualities: maternal sensitivity and non-intrusiveness. Sensitivity refers to how appropriately a mother responds to her baby’s cues, while non-intrusiveness reflects how well a mother allows her baby to take the lead during the interaction without being overly controlling or interfering. Cortisol samples were collected from the mothers at several points during the visit, capturing their average cortisol concentration around the time of the mother-infant interaction.
Following the home visit, the mothers participated in a lab session where they underwent functional magnetic resonance imaging (fMRI) scans. During the scans, the mothers listened to recordings of both their own baby and a control baby crying. These recordings were matched for volume, and the mothers were not told which cry belonged to their own child. The brain scans allowed researchers to measure brain activity in response to the infant cries, focusing on regions known to be involved in auditory processing, emotional regulation, and motor planning.
The findings revealed clear associations between elevated cortisol levels and both brain activity and parenting behavior. Mothers with higher cortisol levels during the home visit were more likely to display intrusive behaviors, meaning they were more likely to take control of the interaction and interfere with the infant’s natural cues.
In terms of brain activity, the fMRI scans showed that higher cortisol levels were linked to reduced activation in several brain regions when the mothers listened to their infants’ cries. These regions included the right precentral gyrus (involved in motor planning), the superior temporal gyrus (which processes auditory information), the medial frontal gyrus (associated with emotional regulation), and the culmen (a cerebellar region linked to early auditory processing). This reduction in brain activity was associated with more intrusive parenting, suggesting that elevated cortisol levels may impair a mother’s ability to respond calmly and effectively to her baby’s distress.
“The most surprising finding was that the interaction of cortisol and the maternal brain occurred primarily in regions of the brain thought to be involved in motor planning and auditory processing, rather than parts of the brain involved in emotion regulation,” Erhart told PsyPost.
“We hypothesized that these emotion regulation regions would be highly associated with cortisol in the context of parenting, and they were not. More research is needed to examine the brain networks involved here — there are techniques that can better elucidate the connection between brain function and subsequent behavior than the region-based activation analysis done in this paper.”
One particularly interesting finding was a three-way interaction observed in the precuneus, a brain region involved in processing self-relevant emotional information. The researchers found that mothers with higher cortisol levels showed reduced activation in this region when listening to their own baby’s cry, compared to a control baby’s cry. This suggests that stress may diminish a mother’s ability to emotionally engage with her own child’s distress, which could lead to more intrusive behavior.
“The take-away point is that we have a better understanding of how our stress system interacts with the maternal brain when responding to infant cry, and how this relates to parenting behavior,” Erhart said. “We know that brain areas responsible for motor planning and auditory processing are the ones that are less engaged with greater cortisol concentration.”
“This study is a first step in understanding the connections between maternal cortisol and the maternal brain and how they together may be associated with intrusive parenting behaviors. Additionally, our study has demonstrated the importance of cortisol levels during the postpartum period, making it a target for further study.”
However, as with all research, there are some caveats. One limitation is the study’s cross-sectional design, meaning that it only provides a snapshot of the relationship between cortisol levels, brain activity, and parenting behavior at one point in time. Because of this, it is not possible to determine whether high cortisol leads to changes in brain function and parenting behavior or whether other factors, such as stress exposure, may cause changes in both cortisol levels and behavior.
“The big caveat is to avoid overgeneralization and over-extrapolation of this research,” Erhart noted. “When examining the relationship between biological systems and behavior, we have to acknowledge that we are discussing how things have been observed ‘on average.’ Biological systems underpinning behavior are complex and multifaceted and often contextually bound. This is especially true when a novel study examines the interrelation of two distinct biological systems. So we are still very much in ‘basic research’ territory, not applied research.”
Despite these limitations, the study offers important new insights into how biological mechanisms, such as the stress hormone cortisol, can shape maternal caregiving behavior. Future research in this area could inform interventions aimed at supporting new mothers, especially those experiencing high levels of stress.
“The long-term goals of this research are to understand how everyday experiences impact the brains of two generations, parent and child,” Erhart explained. “The Family and Child Neuroscience Lab, which pursues this research, has the mission of using psychological and neuroscientific mechanisms to empower families to make informed decisions for their well-being and to impact public health policies.”
The study, “Maternal cortisol concentration is associated with reduced brain activation to infant cry and more intrusive parenting behavior,” was authored by Andrew Erhart, Sarah Watamura, Aviva K. Olsavsky, Alexander Dufford, Rebekah Tribble, Tom Yeh, and Pilyoung Kim.
