In the past decade, researchers have pinpointed a phenomenon in children who have experienced adversity or trauma that can have negative health effects that extend well into adulthood. They call it “toxic stress.”
Toxic stress goes beyond a healthy or tolerable stress response. It is characterized by its intensity and duration. Researchers have labeled three overarching categories of stress:
- Healthy stress is brief and mild-to-moderate in intensity. For example, a child getting a vaccination and then being comforted by a caregiver.
- Tolerable stress response consists of an out-of-the ordinary event — such as a death in the family or a natural disaster — that children are helped through by adults.
- Toxic stress response is prolonged, frequent or intense, and not mitigated by a supportive adult.
Stress can be useful and protective. Think of the “fight-or-flight” response that kicks in when there’s imminent danger: your heart races, you get a boost of energy, your pupils dilate. Those responses are triggered by hormones and neurotransmitters.
But chemical changes in the brain can cause harm if they occur often or for a long time. For example, prolonged exposure to stress hormones can lead to an extended immune system response, which in turn leads to systemic inflammation throughout the body. Prolonged inflammation has been linked with the development of numerous chronic diseases, including diabetes, cancer and asthma, and toxic stress in particular has been linked to diseases including coronary heart disease, stroke, diabetes, cancer and autoimmune disorders.
The landmark 2012 report in Pediatrics that gave toxic stress its name puts it this way: When the body’s biological regulators of the stress response are overly taxed or otherwise imbalanced, this “can lead to a chronic ‘wear and tear’ effect on multiple organ systems, including the brain.”
Stress in childhood is often measured by adverse childhood experiences, or ACEs — a term used to describe difficulties and traumas some children face at home, including household dysfunction, neglect, and physical, psychological and sexual abuse. In other words, ACEs are often the trigger for toxic stress that follows.
But adverse stress reactions can even begin in utero. The American Academy of Pediatrics in August 2019 issued a policy statement titled “The Impact of Racism on Child and Adolescent Health,” which indicates that racial discrimination contributes to maternal stress, which is in turn linked to health complications for infants. The research that follows here looks the health effects of ACEs and toxic stress from kindergarten through adulthood and even into future generations. It also looks at research on potential interventions to improve stress reactions in at-risk groups.
Adverse Experiences in Early Childhood and Kindergarten Outcomes
Jimenez, Manuel E.; et al. Pediatrics, February 2016.
Kids with ACEs before age 5 were more likely to have academic and behavioral problems in kindergarten, this study finds. The researchers looked at a sample of 1,007 children who were part of a national, urban study population – the Fragile Families & Child Wellbeing Study, a 15-year longitudinal study of children born into families at greater risk of breaking up and living in poverty. Most children in the study were born to unmarried parents. ACEs included physical, sexual, and psychological abuse, neglect, and household dysfunction, including substance use, mental illness and incarceration. Teachers of the children in the sample rated the kids’ academic skills and classroom behavior. Over half the group had experienced one ACE; 12% experienced three or more. The group who had experienced three or more ACEs were more likely to have below-average language and literacy skills, attention problems, social problems and aggression compared with kids who had experienced no ACEs. The researchers mention that existing scholarship links poor school achievement to poor health, suggesting that these findings have broader implications beyond the classroom.
Adverse Childhood Experiences in Infancy and Toddlerhood Predict Obesity and Health Outcomes in Middle Childhood
McKelvey, Lorraine M.; Saccente, Jennifer E.; Swindle, Taren M. Childhood Obesity, April 2019.
This study looks at the relationship between ACEs in infancy and toddlerhood on health outcomes later in life. The researchers looked at data covering an 11-year span collected from 1,335 families living in the U.S. The data included family interviews and observational information about ACEs, including emotional, physical and sexual abuse. When the children were 11 years old, the researchers collected information about their height, weight and health status. The researchers found associations between ACEs in early childhood and obesity, respiratory problems, poorer overall health ratings than their peers and regular use of non-ADD/ADHD prescription medication at age 11 (ACEs have already been linked to attention problems, so the researchers were interested in prescription medication taken for non-attention problems). For all health measures, kids with four or more ACEs in early childhood were in the poorest health at age 11. Kids with four or more ACEs had twice the risk of each of the studied health outcomes compared with those who had no ACEs.
Extending the Toxic Stress Model into Adolescence: Profiles of Cortisol Reactivity
Joos, Celina M., Ashley McDonald, and Martha E. Wadsworth. Psychoneuroendocrinology, September 2019.
This study builds upon research on toxic stress by looking at another critical period of development — adolescence. Researchers collected data from 101 adolescents between ages 10 and 12 who lived in urban, low-income households in Harrisburg, Pa. The data included saliva samples, which were analyzed for cortisol levels, and survey responses about sources of stress, family support, personal coping mechanisms and psychological well-being. Cortisol is a stress hormone that can have numerous effects, including suppression of the immune system and increased formation of glucose in the blood. The researchers found signs of toxic stress in adolescence, extending the concept beyond early childhood. Those who were exposed to more community violence and who had less family support did not exhibit normal cortisol level changes in response to stress — an indication of damage to the normal stress response system due to chronic overuse. On the other hand, those who exhibited a normal cortisol response to stress tended to have fewer trauma symptoms.
Adverse Childhood Experiences and Adult Well-Being in a Low-Income, Urban Cohort
Giovanelli, Alison; et al. Pediatrics, April 2016.
This study had two objectives: to determine connections between adverse experiences before the age of 18 and well-being, or lack thereof, in early adulthood, and to test whether a preschool intervention program mitigates such connections. The study followed 1,539 children growing up in disadvantaged neighborhoods of Chicago over more than two decades. The group was 93% African American and 7% Hispanic.
The 989 children in the intervention group attended a preschool program that offered federally-funded educational and family support services, including low child-to-teacher ratios, parent workshops, and health and nutrition services. The control group – the remaining 550 children — attended a typical full-day public school program that did not offer equivalent services. The researchers followed up with the participants when they reached early adulthood (22 to 24 years) to assess whether they experienced ACEs at any point before the age of 18, including the prolonged absence of a parent, death of a parent, divorce of parents, frequent family conflict and being a victim or witness of a violent crime. They measured early adulthood through self-reports of mental health, substance use and occupational status. Researchers used administrative records to measure educational status and criminal behavior, including juvenile arrest and adult felony charges. They found that participants with two or more adverse childhood experiences had significantly worse adult outcomes for the following measures: depression, high school graduation, juvenile arrest, having a felony charge and health-compromising behavior (e.g., smoking and drinking). Further, the preschool early intervention program did not affect the relationship between ACEs and adult well-being outcomes. However, the program was linked to greater educational attainment for those growing up in families with more family-level risk factors (measured by factors including residence in a high-poverty neighborhood, receiving welfare benefits and being raised in a single parent household).
The Association Between Adverse Childhood Experiences and Risk of Cancer in Adulthood: A Systematic Review of the Literature
Holman, Dawn M.; et al. Pediatrics, November 2016.
This literature review looks at existing scholarship about the links between ACEs and cancer risk later in life. The researchers included 12 studies in the review. Seven of the studies were conducted in the U.S., the rest were conducted in Great Britain, Canada, Finland and Saudi Arabia. ACEs included neglect, parental separation or divorce, parental death or serious illness, exposure to domestic violence, physical, psychological, or sexual abuse, and other kinds of adversity or trauma. The researchers find that in all but one of the studies, exposure to ACEs was associated with an increased risk of a cancer diagnosis in adulthood. Of the ACEs included in the review, physical and psychological abuse were most commonly linked with adult cancer risk. Sexual abuse was also linked with heightened cancer risk in two studies. The review is limited in that it does not explain the mechanisms through which ACE exposure might increase cancer risk.
Associations Between Maternal Caregiving and Child Indicators of Toxic Stress Among Multiethnic, Urban Families
Condon, Eileen M.; et al. Journal of Pediatric Health Care, July 2019.
This study looks at the effects of parenting on children’s stress levels. The researchers studied 54 pairs of mothers and children in New Haven, Conn. Participants were recruited through their affiliation with a prior study; all pairs had, in the past, been in the control group of a study testing the effects of an early home visiting intervention for first-time young mothers. They measured indicators of toxic stress — including cortisol levels and levels of immune functioning — in the children’s hair and saliva. Mothers reported their parenting behaviors and completed a survey that provided further insight into their caregiving style, as determined by factors such as interest and curiosity in their child’s mental state. The researchers found that mothers whose behavior was categorized as hostile and coercive — for example, they had agreed with statements such as “I grab or handle my child roughly” and “When I am disappointed in my child’s behavior, I remind him/her about what I’ve done for him/her” — were more likely to have children with behavioral issues. While there were no significant associations between hostile and coercive parenting and biological indicators of toxic stress in children, children whose mothers were more supportive and understanding (per the survey’s measures) had fewer visits to the emergency room.
Parental Adverse Childhood Experiences and Offspring Development at 2 Years of Age
Folger, Alonzo T.; et al. Pediatrics, April 2018.
This study suggests that the effects of toxic stress can be passed down through generations. The researchers looked at 433 parent-child pairs to measure the relationship between adversity or trauma experienced by parents when they were children and developmental delays and eligibility for early intervention services among their offspring. They found that parents who, as children, experienced adversity or trauma, were in fact more likely to have children with an increased risk for developmental delays and eligibility for early intervention services. For example, for each additional maternal ACE, children had an 18% increase in the risk of possibly having a developmental delay. Similar associations held for paternal ACEs. Mothers with three or more ACEs were 2.23 times more likely to have children with a suspected developmental delay compared with mothers who had less than 3 ACEs. And as maternal ACE exposure increased, the number of suspected developmental delays affecting their children increased as well. Fathers with two or more ACES were 4 times more likely to have children with a suspected developmental delay compared with fathers who had one or zero ACEs. The researchers conclude with the suggestion that parental ACEs might be passed down either through genetic means, though this is not examined in the study.
Maternal Adverse Childhood Experiences and Infant Development
Racine, Nicole; et al. Pediatrics, April 2018.
This study focuses on mothers who experienced adversity or trauma when they were children – and the ways this can affect infants’ development. The researchers studied 1,994 women in Canada through pregnancy and until their infants reached 36 months of age. Mothers provided details about ACEs experienced before the age of 18 – including physical, sexual and emotional abuse, as well as family dysfunction. Participants in the sample had between 0 and 4 ACEs. The researchers also screened the infants involved for developmental delays in 5 domains, including communication, gross and fine motor skills, problem solving skills, and personal and social development. Lastly, researchers analyzed measures of maternal physical and mental health to clarify potential pathways through which maternal ACEs impact child development. The researchers found that maternal ACEs were linked to developmental delays for infants.
They suggest these delays might be linked to poor maternal physical and mental health during pregnancy. “Specifically, mothers who experienced more adversity in childhood experienced more health risks in pregnancy and, in turn, had infants who were born with more infant health risks, which were associated with poorer developmental outcomes at 12 months.” The researchers conclude that this indicates a biological framework through which toxic stress is passed down through generations. Maternal stress during pregnancy also was linked to developmental delays, another finding in support of biological factors influencing the transmission of intergenerational health risks. Lastly, after giving birth, mothers who were more hostile as parents were more likely to have infants with developmental delays, which suggests that environmental (e.g., nurture-related factors) also play a role in the transmission of health risks from mothers to children.
Interventions to Improve Cortisol Regulation in Children: A Systematic Review
Slopen, N.; McLaughlin, K. A.; Shonkoff, J.P. Pediatrics, February 2014.
This article reviews the literature on potential interventions to improve biological stress responses in children. The researchers included 19 studies in the review. Each study had control and intervention groups. Eighteen of the studies found differences between baseline cortisol or cortisol reactions between the control group and the intervention group. The design of the studies, however, varied. The researchers suggest a subset of the studies that included an intervention group, a control group, and a third group — a low-risk comparison group — provide the most insight into the effectiveness of interventions. This is because the low-risk comparison group provides a reference for healthy cortisol activity to which the researchers can compare the intervention and control groups. The eight studies with a low-risk comparison group did provide evidence for interventions that helped the experimental group reach healthy cortisol levels (in contrast to the control group). The interventions were all psychosocial interventions – interventions that work to change thoughts and behaviors – that ranged from parenting classes to a stress-management program for mothers. The authors conclude, “Psychosocial interventions hold promise for promoting healthy regulation of physiologic stress-response systems in children and potentially preventing the onset of health problems later in life.”
For more on children’s health, see our roundups of research on how detention centers affect the health of immigrant children and the health effects of screen time.