Exposure to toxic stress in childhood linked to risky behavior and adult disease
How a mother responds to her baby's cries can make a big difference in the child's ability to learn, develop, and thrive. While a warm, supportive response can help the baby calm down and feel secure, a distant or angry reaction leaves the child to fend for herself in a scary world. Over time, the lack of nurturing in the face of adversity in childhood can contribute to "toxic stress"—a harmful level of stress that can affect the child's well-being well into adulthood.
"Toxic stress is the prolonged experience of significant adversity," says Monica Ordway, PhD, APRN, PNP-BC, Assistant Professor at Yale School of Nursing (YSN). Left unchecked, toxic stress in early childhood strains the stress response system and even alters the developing brain. "Over time, without intervention, toxic stress will lead to an increase in adverse health outcomes that would last a lifetime for these children."
What is toxic stress?
The term "toxic stress" refers to stress that is not only overwhelming to a child but also not alleviated by the buffering of supportive adults. A concept developed by the National Scientific Council on the Developing Child, toxic stress describes the body's response to negative events or experiences that are either powerful, repeated, or prolonged. A child who routinely suffers abuse, neglect, or other forms of hardship, such as poverty, may be at risk for this harmful form of stress.
Toxic stress has gained attention in recent years as advances in the areas of epigenetics, neuroscience, and life-course science have all pointed to it as a source of poor outcomes for children and adults. "This is a rapidly evolving field," says Andrew Garner, MD, PhD, FAAP, a primary care pediatrician at University Hospitals Medical Practices in Cleveland. He explains that experts in developmental science have long understood that catastrophic events, such as experiencing or witnessing trauma, have negative effects on children. But now "people are beginning to realize that there is a spectrum of childhood adversity," says Garner. Family circumstances that were considered routine—such as divorce or separation, parental mental illness or substance abuse, or growing up in poverty—are anything but. "Whether the adversity is catastrophic or more routine and mundane, the effect on the body is similar. There's that common denominator of the physiologic stress response," he explains.
When stress is positive or tolerable—a child gets an immunization or starts day care—the proverbial "fight-or-flight response" kicks in temporarily. The fight-or-flight response, in which stress hormones rise and inflammation increases, is healthy and crucial for survival. But when the stress response is prolonged and not eased by caregiver support, it becomes toxic to the brain and other organ systems, according to a report co-authored by Garner et al., and published in Pediatrics. The part of the brain that triggers the stress response (the amygdala) may become overdeveloped and overactive, while other areas of the brain that govern memory, learning, and decision-making underdevelop. "Most worrisome," says Lois Sadler, PhD, RN, PNPBC, FAAN, Professor at YSN, "is that areas like the prefrontal cortex, which is where we do most of our thinking and decisionmaking, may not become as developed as the other, more emotion-regulated parts of the brain." The combination leaves young children with a chronically heightened stress response system.
These changes in the brain's architecture and functioning can have far-reaching effects. In a child chronically exposed to toxic levels of stress, the changes may result in chronic anxiety, learning delays, or poor social skills. Over time, toxic stress affects behavior and lifelong health. "Some of the effects of toxic stress are more immediate, and some are more delayed responses that may not show up until later," Sadler explains
Adversity and its effects
No one knows how many children experience toxic stress, but a growing body of research on "adverse childhood experiences" suggest that it may be common. In the late 1990s, the Centers for Disease Control and Prevention collaborated with Kaiser Permanente to conduct the Adverse Childhood Experiences (ACE) study. The research on more than 17,000 adults found that those who had experienced abuse, neglect, or family dysfunction during childhood were more likely to develop unhealthy behaviors and serious disease in adulthood. "What we found in the ACE study was that in a clearly middle-class population—which made it even more unexpected—a remarkable number of people had had toxic life experiences in childhood that were still playing out roughly a half century later," says Vincent Felitti, MD, an internist at Kaiser Permanente and co–principal investigator of the ACE study.
More than one in four adults surveyed had experienced at least one of the childhood adversities, and one in eight reported four or more ACEs, including emotional, physical, or sexual abuse; emotional or physical neglect; and household dysfunction (divorce or separation, domestic violence, parental substance abuse, parental mental illness, and an incarcerated family member). The most common ACE was physical abuse, reported by 28.3 percent of adults. "What we found in a general population was that in fact ACEs were remarkably common and remarkably destructive," Felitti says. ACEs are linked to both risky behavior and adult disease. According to one paper published in American Journal of Preventive Medicine, people who experienced four or more ACEs were more likely to be at risk for alcoholism, drug abuse, depression, and suicide. They were more inclined to smoke, and be inactive and obese. Most disturbingly, those who suffered the most adversity in childhood were more likely to develop diseases such as ischemic heart disease, cancer, chronic lung disease, skeletal fractures, and liver disease.
The original ACE study findings were recently confirmed by a follow-up study released in late 2014 by the Center for Youth Wellness and the Public Health Institute. The study report, "A Hidden Crisis: Findings on Adverse Childhood Experiences in California," found that a majority of more than 27,000 adults surveyed, or nearly 62 percent, had experienced one or more types of childhood adversity. The research confirmed the link between four or more ACEs and disease, such as asthma, stroke, and depression. It also found that those who endured the most childhood adversity were at risk for other poor life outcomes, including poverty, unemployment, and lack of health insurance.
These data are mirrored by what nurse practitioners like Ordway have seen in practice. She cites poverty, food insecurity, and even maternal depression as examples of factors that contribute to childhood adversity and toxic stress in families. "Single parenthood can place financial strain and burden on the parent that often increases their level of stress, which impacts the child," she says. Even in two-parent households, long hours and job insecurity can take a toll and interfere with the ability of the caregiver to provide the type of supportive, responsive environment that would otherwise buffer stress.
Additional forms of adversity may include environmental factors like violent crime or gang activity at the neighborhood or community level, notes Sadler. Inside the home, open conflict between parents, the presence of transient or intoxicated family members, and exposure to violent media could undermine a child's ability to feel safe. What the science has demonstrated is that the impact of these exposures, and the toxic stress that follows, is not benign. "When we start talking about changes in the way the genome works, the way the brain architecture is formed, that helps people begin to understand the way early childhood experiences are literally embedded in the body," says Garner, "and therefore strongly influence behaviors, productivity, and health down the line."
Solutions to toxic stress
Child development experts may not be able to eliminate the triggers of toxic stress—poverty, neglect, abuse—but they can help support families from the prenatal stage onward. "What's the thing that tends to prevent toxic stress? It looks like it's safe, stable, and nurturing relationships," says Garner. With the support of a caring adult, a child's stress response can return to normal, even in the face of significant adversity such as divorce or death of a family member. The presence of protective adults makes it possible for a young child to adapt to stress in healthy ways that facilitate growth and healthy development.
One effective strategy for helping new parents build the skills they need to buffer stress for their children is home visits from nurses and other providers. For example, the Minding the Baby (MTB) program, developed by Sadler and her colleagues at the Yale Child Study Center, Fair Haven Community Health Center, and the Cornell Scott Hill Health Center in New Haven, is an evidence-based intervention that begins with mothers at the prenatal stage. From the third trimester up to age two, pediatric nurse practitioners and clinical social workers visit mothers—typically teenage parents—in the home environment to provide health and mental health care. By intervening early, MTB nurses target two generations—the stressed-out young mother and later, her child. "It's a double layer of trying to help parents understand their own responses and their own underlying feelings that may be coloring the way they interact with their child, as well as trying to understand the child," says Sadler.
Parents who are overwhelmed by their own challenges are often less equipped to offer the care and support children need to handle adversity. "Often caregivers have the right intentions but they did not experience positive parenting as a child themselves to prepare them to parent their own children," notes Ordway. A mother who grew up experiencing toxic stress as a child may still be coping with the effects or have few positive parenting examples to draw from. "There's an intergenerational issue here, where they're raising their children the way they were raised, so there was often no role model to show how to sit and talk to the child about their feelings or emotions," Ordway adds.
Home visiting programs address these intergenerational issues. In the MTB program, through a process called "parental reflective functioning," young mothers learn to better understand the feelings, intentions, and needs that underlie their own behaviors and those of their child. "It's a gradual process because it's a different way of thinking about themselves and their children than they have probably ever done before," she notes. New mothers who reflect not only on their own feelings, but also on the developmental needs and emotions of their fussy babies, are better able to respond positively. "That helps them be more sensitive to what the baby might needor to try different things," says Sadler.
Research on home visiting programs shows they work. In a paper published last year, Sadler et al. found that children in the MTB program are much more likely to develop secure attachments to their mother. "What we're hoping is that this secure attachment in a high percentage of families is going to work like a protective shield against the toxic stress that they are encountering in their lives," says Sadler. "That is, 'yeah, scary things can be happening, but mom's going to make it okay.'" Another well-known home visiting program, the Nurse Family Partnership, has shown many positive results for children and families.
Working with Sadler, Nancy Redeker, PhD, RN, FAHA, FAAN (YSN's Beatrice Renfield Term Professor of Nursing, Director of the school's Biobehavioral Laboratory, and Professor at Yale School of Medicine's Department of Internal Medicine), and a pediatric sleep working group, Ordway is exploring additional interventions that could be applied by primary care providers, either in a medical home or in private practice. Specifically, they are looking into ways to help improve the sleep patterns of children and parents. "We know that the same health outcomes experienced by children exposed to toxic stress are similar to what we see in children who experience sleep deprivation or poor sleep quality, leading to poor health outcome risk," says Ordway. "One of the theories we have is if we can support parents to develop healthier sleep quality, better sleep duration for children, that may be a way of buffering the effects of toxic stress."
To effectively address toxic stress, however, both Sadler and Ordway explain that multiple interventions are essential. "There's a need for different kinds of programs that fit the particular needs of families or communities," says Sadler. Some individuals may have specific needs that fit well with components or strengths of particular interventions. Certain families may need to participate in an intensive home visiting program, while others might benefit from a sleep intervention provided in a pediatric or family primary care setting. "A diverse menu of interventions will be most successful," Ordway adds.
Garner describes a range of possible interventions that reflect a comprehensive public health approach—from evidencebased therapies to treat those children who have experienced trauma to targeted interventions that would screen and identify those at risk. Parenting programs and early intervention programs can help address the problem before children start to experience the effects of toxic stress, such as developmental delays. Another public-health-oriented approach, he notes, would be some form of universal primary prevention that all children receive, such as social-emotional learning in school. "Our real long-term goal is to help kids build skills so that when they have adversity, they deal with it in an effective manner," he says. "If we can somehow find a way to make adversity more tolerable or even positive so those experiences are opportunities to learn and grow, that's what we're trying to do."
The role of nurses
Nurses are already on the front lines in the battle against the negative effects of toxic stress. From prevention, intervention, and treatment, nurses often spend more time with patients in different settings and have opportunities to minimize the impact of adversity on children and families. Whether they are registered nurses, nurse coordinators, nurse practitioners, or nurse researchers, nurses across disciplines play a key role in identifying those at risk and developing the most effective interventions.
To support families, nurses can also work in interdisciplinary teams. "We're really good at doing that as nurses," notes Ordway. "The most successful programs will incorporate an interdisciplinary approach—social work, nurses, physicians all together working to identify how we can better support these families."
Nurses can also have an impact by raising awareness and influencing policy. "I think, as nurses, we also need to be very active in changing some of the governmental policies around how we support families," says Ordway. One example, Ordway notes, is to advocate for policy change that would allow nurses to refer families with depressed mothers because of the link between maternal depression and adverse childhood outcomes. "That's a policy that as nurses we can impact," she explains.
Lois S. Sadler et al. Minding the Baby: Enhancing Reflectiveness to Improve Early Health and Relationship Outcomes in an Interdisciplinary Home-Visiting Program, Infant Mental Health Journal (2013). DOI: 10.1002/imhj.21406