in a community where hugs are common and affectionate might consider hugs from caregivers to be a positive experience, and there is ample evidence that close physical contact with a trusted caregiver can be both reassuring and regulating for children (see, e.g., Forkey et al., 2021; Nelson & Gabard-Durnam, 2020). But if a child has experienced abuse at the hands of a caregiver, hugs might trigger emotional distress and biological stress responses. Making distinctions between “positive” and “negative” experiences can be difficult without considering the meaning or narrative that an individual child attributes to those events or assessing the biological response to those events (Lopez et al., 2021; see this chapter’s brief discussion of toxic stress).

Third, statistical associations at the population level cannot speak to patterns for any individual, and associations can never prove causality. For example, some children experience significant adversity in childhood but nevertheless are healthy, happy, and productive adults (Baldwin et al., 2021). Conversely, some children have significant advantages in childhood yet struggle as adolescents or adults (Luthar & Latendresse, 2005). Associations might point toward some salient features of the early childhood ecology that may influence, directly or indirectly, the outcomes of interest—but these associations are rarely perfect. They therefore confer a degree of risk that is observed and calculated at the population level. Determining an individual’s true level of risk requires a much broader assessment of not only their risks but also their protective factors. Protective factors are characteristics, conditions, and circumstances that both (a) reduce the effect of exposure to risk factors and stressful life events, thereby decreasing the likelihood of negative outcomes, and (b) promote healthy development and well-being, thereby increasing the likelihood of positive outcomes (Bethell, Gombojav, & Whitaker, 2019). In sum, childhood is not destiny, but childhood experiences provide a foundation for future growth and development.

RELATIONSHIPS AS BIOLOGICALLY NECESSARY

As summarized by Tottenham (2025, p. 2) in a memo to the committee, from an evolutionary perspective, human infants are born neurologically immature and require prolonged caregiving for survival and healthy brain development (see also Silk et al., 2003; Tottenham, 2020). Attachment serves as an evolutionary mechanism for human infants that emerged to ensure survival of the infant and its health (Bowlby, 1969). The human brain evolved in the context of close social bonds, where caregiver presence served as a biological regulator of infant physiology (e.g., stress response, emotional regulation; Hofer, 1994).

Although the precise biological mechanisms underlying these positive emotional connections remain to be clarified, biobehavioral synchrony likely plays a role (Abraham & Feldman, 2018; Abraham et al., 2021; Endevelt-Shapira

& Feldman, 2023; Feldman, 2017, 2020; Shimon-Raz et al., 2023; Ulmer Yaniv et al., 2021). Biobehavioral synchrony refers to the coordination of brain waves, autonomic functions, hormonal levels, and behaviors that occurs when there is a deep emotional connection between individuals (Feldman, 2017). It is the temporal coordination of cardiac, neural, and/or behavioral signals between two or more individuals (e.g., among adults and/or children) while they engage in mutual experiences (Kingsbury & Hong, 2020; Liu et al., 2018; Madsen & Parra, 2022). Biobehavioral synchrony can occur across the life course and across relational partners beyond the parent/caregiver–infant/child relationship (Konrad & Puetz, 2024; Yoon et al., 2021).

Feldman (2015) developed the biobehavioral synchrony conceptional model, providing strong support for the hypothesis that mother–infant biobehavioral synchrony experienced repeatedly in the first year of life is a critical environmental input for building social-emotional skills (Atzil & Gendron, 2017; Bell, 2020; Feldman, 2015, 2017; Leclère et al., 2014; Ulmer Yaniv et al., 2021).¹ Studies of mother–infant dyads provide mounting evidence that the dyads reach biobehavioral synchrony during reciprocal face-to-face interactions in some cultural settings (Beebe & Steele, 2013; Endevelt-Shapira & Feldman, 2023; Endevelt-Shapira et al., 2021; Feldman, 2011; McFarland et al., 2020; Morgan et al., 2023). As noted by many experts, variability in the types of synchrony (e.g., continuous vs. sequential, coherence vs. phase synchronization; Turk, Endevelt-Shapira, et al., 2022; Turk, Vroomen, et al., 2022) and frequency bands analyzed (Bell, 2020) limits interpretability of results across studies.

More recently, the construct of emotional connection emerged (Welch et al., 2015) as a behavioral measure of the emergent property resulting from reciprocal mother–infant emotional attunement during a face-to-face interaction. In one study of 15 mother–infant dyads, the mother’s expression of positive emotions was associated with stronger 6–9 Hz range interbrain network connectivity; the findings suggest that the parent–infant interbrain network is modulated by the emotional quality and tone of dyadic social interactions (Santamaria et al., 2020). Using functional near-infrared spectroscopy, a study of 41 dyads showed that similar levels of positive affect in mother and infant during toy-led play are correlated with synchrony in the medial/lateral frontal and temporoparietal brain regions (Morgan et al., 2023). Across cultures, emotions play a central role in how infants communicate with their caregivers and vice versa (Boeve et al., 2019; Broesch et al., 2022). Emotional

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¹ The Center on the Developing Child (2025) at Harvard University popularized the concept of serve and return, defined as responsive, back-and-forth exchanges between a young child and a caring adult, which play a key role in shaping brain architecture. Biobehavioral synchrony can be observed in serve-and-return interactions (Tronick & Gold, 2020; Zuckerman & Tronick, 2023).

states trigger inner-body sensations, which have been shown to play a mediating role in dyadic interactions (Blain et al., 2025; Suga et al., 2022).

Cycles of Relating, Rupture, and Repair

One reason relational health is hard to define and quantify is that it is not a static state but a dynamic process, with connections inevitably waxing and waning over time. A mutually rewarding relationship might become hurtful or toxic for one or more parties in a moment or days, weeks, months, or years later. That is, the biobehavioral synchrony that exists between individuals is dynamic, with ongoing cycles of relating, rupture, and repair (Garner & Saul, 2025).

In the context of children’s early relationships, products of repair including trust, affect regulation, the infant/child’s experience of self-agency, and the learning that both caregiver/parent and infant/child gain about each other’s and their own self-regulation capacities and needs are foundational for social learning (Garner & Saul, 2025). Using micro-analytical methods, Beebe showed that mother–infant interactions are defined by a continuous process of mismatch and repair, which is predictive of later social-emotional outcomes (Beebe & Steele, 2013; Beebe et al., 2010). Breaches, ruptures, and disconnects are inevitable and may actually be necessary to allow for opportunities to practice interactive repair (Tronick & Gold, 2020). As Tronick and Gold (2020) emphasize, it is not the rupture itself but the inability to repair that can create harm. Over time, the expectation of repair builds trust and the ability to handle distress in a healthy manner (Müller et al., 2022). Such repairs repeatedly convey a mutual commitment to understanding each other and to remaining connected As summarized in Garner and Saul (2025, pp. 3-31), “We are programmed to connect with others, and it feels great when we do; life inevitably gets in the way, and we will feel disconnected and stressed; but the speedy restoration of synchrony—even if only for a moment or two—turns off the body’s stress response. From a strictly biological standpoint, buffering adversity is all about the repair.”

EARLY SENSITIVE PERIOD OF DEVELOPMENT

Relational health begins in preconception, continues prenatally, and evolves throughout the lifespan. However, there is a sensitive period early in life when the biological systems that are necessary to support optimal life course relational health develop. Sensitive periods are times when the developing neural circuits are most sensitive to environmental input. Early relational experiences—and the neural activity that they generate—have the potential to become biologically embedded, influencing both early brain development and long-term functioning (Delgado et al., 2006; Nelson &

Gabard-Durnam, 2020; Reh et al., 2020). Research suggests that early childhood is a sensitive period; while brain circuits continue to develop into adolescence and healing can continue throughout the lifespan (Tottenham & Galván, 2016), early experiences exert a disproportionate influence on the child’s well-being because of the brain’s heightened plasticity in infancy and early childhood (Nelson & Gabard-Durnam, 2020; Shonkoff, 2016; Shonkoff et al., 2012).

Neurobiologically, adverse early caregiving experiences are associated with altered development of both subcortical regions (e.g., amygdala, hippocampus, striatum) and the prefrontal cortex. For example, early adverse caregiving has been associated with heightened amygdala reactivity to emotional stimuli, indicating increased sensitivity to potential threats or stressors (e.g., Gee et al., 2013; McLaughlin et al., 2019). Adverse caregiving is also associated with disrupted connections between the amygdala and prefrontal cortex, which play a critical role in top-down regulation of emotion (e.g., Gee et al., 2013). Alterations to these circuits confer increased vulnerability to anxiety, depression, and dysregulated stress physiology (e.g., Gee et al., 2013; Hanson et al., 2015; Herringa et al., 2013).

Studies of children living in orphanages suggest a very early period of sensitivity for development of relational processes; findings show children ranging in ages of approximately 6−18 months may be especially sensitive to deficiencies in environments (see, e.g., Gunnar, 2001; MacLean, 2003; Merz & McCall, 2007; Rutter et al., 2007; St. Petersburg-USA Orphanage Research Team, 2008). In a randomized controlled study examining children living in a Romanian orphanage, Nelson et al. (2019) found that placing children into foster care before age 2 years significantly enhanced recovery from the deficient environment, whereas removal from the institutionalized setting after approximately age 2 years showed diminished outcomes, especially in social, cognitive, and emotional domains, though these findings focus on highly deprived orphanage contexts and may not be broadly generalizable.² According to Tottenham (2025), this body of

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² According to Nelson et al. (2019), “Clear timing effects were apparent at younger ages—those placed into families before 2 years of age fared better than those placed after 2 years of age—but in several domains these timing effects disappeared by the time children were 8 to 12 years old. [. . .] More importantly, however, intervention effects were maintained. [. . .] One possible explanation is compensatory processes in brain development that allow some recovery of function through alternative pathways/neural circuits despite early disturbances in brain architecture. [. . .] This argues for a sensitive period interpretation of the findings—that is, prolonged and continuous effort (i.e., living in a high-quality foster care family for many years) may overwrite the effects of early deprivation—but only in some domains. Another possibility is that early deprivation temporally extended the sensitive period, making it possible that later placed children continued to accrue benefits compared to the children who experienced care as usual. Better understanding of the development of specific circuits and their sensitivity to environmental input in humans will help clarify these findings” (p. 8).

work underscores the significant impact of early caregiving experiences on neurodevelopment, highlighting sensitive periods during which the brain is particularly susceptible to environmental input (see also Teicher et al., 2016; Tomoda et al., 2024; Tottenham, 2020).

MOMENTS OF CONNECTION

The committee defines early relational health broadly as encompassing mutual, meaningful, and affirming moments of genuine connection and belonging. Related yet distinct relational concepts include secure attachments; caregiver sensitivity; interactions with mutuality; shared attunement; biobehavioral synchrony; family resilience and connection; positive or benevolent childhood experiences; and safe, stable, and nurturing relationships. These diverse theoretical constructs ultimately converge in their shared objective of describing distinct facets of relationships that develop over time through moments of connection. Moments of connection can occur in any of the places where children spend their time, such as in families, care settings of various types, and the broader community. Box 2-1 provides a descriptive vignette of moment-by-moment interactions between an infant and caregivers.

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³ Overall, the relationship between the various early relational health constructs used in the literature to describe and understand moments of connection (including those described above) and the unique contribution they bring to the promotion of various child developmental out-

include Cordolcini et al., 2024; Gettler et al., 2021; Storey et al., 2020). Additional research is needed; see Chapter 6.

Bonding and Attachment

Many early relational health constructs in the literature describe maternal feelings (bonding), or maternal and infant/child behaviors during face-to-face, play, or caregiving interactions. Bonding was first described by Klaus and Kenell (1982) as a mother-driven concept describing the mother–infant emotional tie that begins forming during pregnancy and continues beyond birth (Barker et al., 2017; Bicking Kinsey & Hupcey, 2013; Hill & Flanagan, 2020). Child attachment was first proposed by Bowlby (1969); it describes children’s internal working models of their caregiver (Bretherton, 1992; Cassidy & Shaver, 2016). Child attachment is usually assessed at ages 12–18 months with the observer-based Strange Situation Procedure (Ainsworth et al., 1978), which categorizes infants (ages 9–30 months) by attachment style—secure, avoidant, ambivalent/resistant, disorganized—based on their responses to caregiver separations and reunion.

Intersubjectivity and Shared Intentionality

Trevarthen (2011, 2015) and Trevarthen and Aitken (2001) describe and document the complex meaning-making process that occurs between an infant and caregiver in a process termed intersubjectivity. Intersubjectivity is one aspect of the very young infant’s contribution to the dynamic processes of early relationships and is the development of active “self-and-other” awareness in infancy (Trevarthen & Aitken, 2001, p. 3). Trevarthen (2017) documented careful analysis of a video of a blind 5-month-old infant; in the video, the child “conducted” a familiar folk song while the infant’s mother sang to the infant. Trevarthen (2017) documented how at moments the infant anticipates the song (moving its hand one-third of a second ahead of the mother’s voice). Trevarthen analogizes the interaction to jazz improvisation, where the leadership shifts back and forth with moments of synchrony in between.

Tomasello, in the book Becoming Human (2019), builds on the understanding of intersubjectivity and describes that the ability to recognize each other’s intentions is central to our humanness. Tomasello (2019) points out that the first 9 months of life offer a kind of gestation of shared intentionality as parent and infant move through micromoments of misunderstanding to understanding. This process of meaning-making begins as soon as the infant and caregiver meet and engage in the complex, moment-by-moment process of getting to know each other (Gold, 2025).

of repair, and eventually to the child (self-regulation). Emotional regulation is a functional component of empathy because it is needed for someone to witness harm without being harmed (Decety & Holvoet, 2021).

MANIFESTATIONS OF EARLY RELATIONAL HEALTH

While relationships and early relational health are a universal human need, universality does not mean uniformity (Hilton et al., 2022; Mesman et al., 2018). Early relational health manifests in person-, family-, and community-specific ways. That is, human development requires relational health, but it is experienced differently by each individual, and communities vary in how they achieve strong attachments with children (Mesman et al., 2016; Van Ijzendoorn & Kroonenberg, 1988). As Barrett (2017b) and others have shown, emotions are concepts constructed through interaction and culture. Caregivers teach children, both implicitly and explicitly, how to interpret bodily sensations and contextual cues to construct meaning and emotional understanding within the community and cultural context. Batja Mesquita’s (2022) Between Us, for example, shows that emotions are not fixed, universal experiences; instead, they are shaped within relationships and family and community contexts. What we feel, express, and value emerges from the social worlds we inhabit—what Mesquita (2022) terms mine versus our emotions.

Although nurturing relationships and secure attachment are often conceptualized between a primary caregiver and child, it is important to note cultural differences and conceptualizations of attachment and positive interactions that may reflect more communal and extended caregiving relationships (Choate & Tortorelli, 2022; Titcomb et al., 2019). These differences in attachment and communal caregiving relationships differ from European-heritage communities (Morelli et al., 2017; Rogoff, 2003), underscoring the need for conceptual models and measures of early child development that reflect different cultural knowledge, values, beliefs, practices, and skills, as well as ways of living, knowing, and thinking about the world, particularly about what children need to develop optimally.

A high level of microscale synchrony has also been found among Indigenous-heritage children in peer, family, and teacher–child relationships (Alcalá et al., 2018; Erickson & Mohatt, 1982; Mejía-Arauz et al., 2007). For example, in microscale observations of family interactions coded in 200-millisecond segments, Dayton et al. (2022) found that Guatemalan Mayan mothers with two children ages 1 and 3 to 5 years engaged mutually with both children, in fluid synchrony, more often than European-American middle-class triads in the same situation (exploring novel objects). The Mayan families spent almost all their time engaging mutually in fluid synchrony

among all three people, whereas the middle-class European-American families spent most of their time with two people engaged together and one left out with no one mutually engaged with another person, or in conflict with each other (Dayton et al., 2022). Overall, the Mayan children spent more time in synchronous interaction with their mothers than European-American middle-class children (Dayton et al., 2022).

In many communities, orienting infants and young children toward the broader social world is the goal, not fostering exclusive one-on-one relations (e.g., Morelli & Tronick, 2013; Ochs, 1982). Relatedly, children’s relations with other children are likely to be relatives of different ages, unlike in middle-class, European-heritage communities—where much of the research on early child development has occurred—where children’s relations with other children are more likely to involve same-age peers (Morelli et al., 2003). By contrast, in many communities, older children care skillfully for younger children (Weisner, 2014) and share close, supportive relationships. Important variation across cultural communities includes which partners matter (mother, father, grandpa, older sister, etc.). For example, central to the socialization of Black American children at all income levels is valuing and promoting extended family relationships—that is, connections with cousins, grandparents, aunts, uncles, and fictive kin (i.e., nonbiologically or nonlegally related but family-like individuals; Hays & Mindel, 1973; Hill, 1999; Mollborn et al., 2011; Sudarkasa, 1997). Extended family relationships provide social-emotional and child-rearing support for both children and parents, practical resources, and a sense of cultural connectedness that can provide children with a sense of rootedness and help mitigate the negative impacts of racism-related stress (Hill, 1972; Iruka et al., 2025; Murry et al., 2023).

Some communities, even at the start of life, conceive of children as in relationship, not arriving as independent units that need to learn to be in relationship (Fogel, 2001; Trevarthen, 2014). This understanding of children being born already in deep relationship is exemplified by the belief among some Native American communities that infants arrive as spirit beings, emerging not from a place of isolation but from one of connection with the spiritual realm from which they came (Ward et al., 2022). An assumption that infants arrive as independent units may relate to the prevalent separation in middle-class life of young children from the lives of their families and communities into age-segregated care apart from their families and communities (Morelli et al., 2003).

THE IMPACT OF EARLY RELATIONAL HEALTH

Drawing from the available literature, the sections below provide an overview of what is known about associations between early relational

health and children’s outcomes, though it is not exhaustive. Overall, the committee found that early relational health benefits children, families, and communities, shaping pathways for health and well-being across the life course. Specifically, early relational health is associated with positive psychological, social, and physical health outcomes. Of note, these conclusions are based on an evidence base consisting primarily of correlational studies, which cannot speak to causality. Nonetheless, the wide range of methodologies used in these studies—including retrospective, cross-sectional, and longitudinal study designs; self-report, observational, and biomarker data; and meta-analyses with thousands of participants—and consistency across multiple studies increase confidence in these conclusions. The sections that follow discuss the two main pathways by which early relational health is associated with children’s outcomes: (a) by predicting children’s short- and long-term outcomes and (b) by buffering the effects of stress on children.

Early Relational Health and Children’s Health and Well-Being

A large body of research has provided clear evidence for linkages between early relational health and children’s short- and long-term health and well-being. Overall, better early relational health is associated with positive outcomes in multiple domains, including (a) social-emotional wellbeing and mental health, (b) relational outcomes, and (c) physical health.

Regarding children’s social-emotional well-being and mental health outcomes, meta-analyses show that children with more secure attachments to their parents (as highlighted above, one indicator of early relational health) have less negative temperaments (Groh et al., 2017), fewer internalizing and externalizing behaviors (Dagan et al., 2021; Deneault et al., 2021; Madigan et al., 2013, 2016), and fewer attention problems (Pallini et al., 2019). Meta-analysis of studies of observed parental sensitivity and child behavioral problems has also shown that higher parental sensitivity is significantly associated with fewer child internalizing and externalizing problems (Cooke et al., 2022). Other research indicates that adults reported lower prevalence of depression and/or poor mental health when they retrospectively reported that as a child, they were able to talk to their family about their feelings, felt their family stood by them during difficult times, felt safe and protected by an adult in their home, and had at least two nonparent adults who took an interest in them (Bethell, Jones, et al., 2019).

There are also robust linkages between better early relational health and more positive relational outcomes. Meta-analyses show significant associations between young children’s secure attachment and greater social competence with their peers during childhood (Groh et al., 2014), and

between young children’s secure attachment and later increased prosociality (e.g., empathic responding; helping, sharing, and caring behaviors; cooperation; Deneault et al., 2023). Additionally, having a secure parent–child attachment is associated with less anxious and avoidant attachments as an adult (see meta-analysis by S.-H. Kim et al., 2021). More broadly, in a scoping review, Painter et al. (2025) analyzed prospective associations between early relational health during ages 0–3 years and children’s relational outcomes during early childhood (4–6 years), middle childhood (7–11 years), adolescence (12–17 years), and early adulthood (18–35 years). That review demonstrated evidence of significant associations between early relational health and the quality of children’s later relationships with their family, friends, and romantic partners.

Finally, there is a growing body of research examining linkages between early relational health and later physical health outcomes (for additional discussion, see Ehrlich & Cassidy, 2021). These studies have included different indicators of early relational health, different follow-up periods, and different health outcomes, but they are consistent in suggesting linkages between better early relational health and better physical health. For example, early in development, maternal sensitivity at infant age 5 weeks predicted lower rates of infant respiratory symptoms and skin conditions (though not infant digestive or general illnesses) over the first year (Stern et al., 2020). Another study found that early maternal sensitivity over the first 3.5 years predicted lower cardiometabolic risk (a composite index including blood pressure, body mass index, waist-to-hip ratio, c-reactive protein) at age 37 years (Farrell et al., 2019). Farrell et al.’s (2019) findings are especially notable given the documented link between early relational health and health biomarkers more than 30 years later. Another study used data from the same sample and found that infants with more secure attachments self-reported less physical illness at age 32 years (Puig et al., 2013).

Furthermore, as Tottenham (2025) described to the committee, early caregiving quality is associated with cardiovascular functioning, inflammatory processes, and stress hormone regulation via the hypothalamic–pituitary–adrenal axis (e.g., Anderson et al., 2018; Carroll et al., 2013; Chen et al., 2011; Dozier et al., 2008). These findings are supported by meta-analyses involving thousands of children, which confirm the strength and reliability of these effects (Fearon et al., 2010; Groh et al., 2014). Importantly, evidence from randomized controlled trials has established that these links are not merely correlational. For example, the Attachment and Biobehavioral Catch-up intervention, an attachment-focused parenting intervention that encourages nurturing caregiving, has been shown to causally improve children’s stress physiology and cognitive development (Garnett et al., 2020; Lind et al., 2017).

become biologically embedded and influence gene expression decades later (Garner & Saul, 2025; Zhang & Meaney, 2010).

Much of what we currently know about the early embedding of childhood experiences comes from work on negative experiences and their associations with negative outcomes. For example, when the body’s stress response system is activated, usually in response to activation of the amygdala, it increases downstream mediators of stress such as epinephrine and cortisol (Shonkoff et al., 2012). In the short term, these mediators are adaptive, preparing the body for “flight or fight.” When the threat has passed or social-emotional buffers are present, the activation of the body’s stress response is brief, and the body returns to baseline functioning. But if the threat persists or there are insufficient social-emotional buffers, the downstream mediators persist and can become maladaptive or “toxic” (Center on the Developing Child, 2010). The term toxic stress therefore refers to the body’s response to continuous or unpredictable threats or adversity.

The concept of toxic stress begins to explain how negative experiences in childhood might induce long-lasting changes in both the brain and the genome (McGowan et al., 2009; Oberlander et al., 2008; Wiggins et al., 2014). It is important to note that although methylation patterns can remain quite stable over the lifespan, there is some evidence that they can be altered by experience. For example, a mother’s tender touch can reverse the methylation of the newborn’s glucocorticoid receptor gene (Murgatroyd et al., 2009).

Similarly, toxic stress responses in childhood can lead to a relative mismatch between the amygdala and the prefrontal cortex; these sites are particularly vulnerable to toxic stress because they are rich in glucocorticoid receptors (de Kloet et al., 2019). Such a mismatch can lead to issues with emotional regulation, abstract thought, and working memory (Sapolsky, 2017; Shonkoff et al., 2012). It is important to note that all these functions of the prefrontal cortex are integral to making and sustaining healthy relationships (Bickart et al., 2014).

Moreover, neurocognitive changes—particularly in threat, reward, and autobiographical memory systems—can lead to “social thinning” (a reduction in meaningful social relationships) and “stress generation” (increased risk of interpersonal stress due to maladaptive behavior patterns; McCrory et al., 2022). These processes are autocatalytic and transactional: they evolve dynamically through interactions between the child and their environment. When left unaddressed, they may create a feedback loop of stress, isolation, and psychiatric vulnerability. However, when relational supports and neurodevelopmental protective factors are in place, these same systems can recalibrate toward adaptive trajectories. Importantly, the concept of social thinning offers a developmental and neurobiological explanation for

how social isolation and loneliness can emerge early in life—well before they are recognized in adolescence or adulthood (McCrory et al., 2022).

Although toxic stress responses—sustained exposure to the physiologic mediators of stress due to persistent or extreme adversity in the absence of adequate social-emotional protective factors—might explain some of the associations between adverse childhood experiences and poor outcomes decades later, adverse childhood experiences and toxic stress are not synonymous. Adverse childhood experiences are a subset of the potential negative childhood experiences that might trigger a toxic stress response; they are known to be associated with negative developmental outcomes at the population level. Whether a childhood experience triggers a toxic stress response at the individual level depends on other factors. In particular, the presence of protective factors can mitigate toxic stress responses, the associated physiological changes, and the negative outcomes even in the presence of significant or sustained adversity (see, for example, Baldwin et al., 2021).

Early Relational Health as a Buffer

As the previous discussion highlights, the presence or absence of positive relationships is thought to play a critical role in determining whether a stressor is tolerable or toxic. There is growing evidence that early relational health—and positive relationships during childhood more generally—can serve this type of protective role (for review and discussion, see Chen et al., 2017; Gee & Cohodes, 2023; Gunnar, 2017). Considered across a number of samples, stressors, and indicators, there is increasing evidence that early relational health can protect against the adverse effects of stress on children’s stress biology, physical health, and psychosocial functioning. Nonetheless, the committee again cautions that most of these studies used correlational study designs that cannot speak to causality.

Caregivers shape children’s long-term capacity for resilience by co-regulating their emotions until the children are developmentally able to self-regulate (Feldman, 2007; Hofer, 1994; Tronick, 2018; Waters et al., 2024). Such early caregiving has powerful effects on children’s emotional learning, stress physiology, and mental health (Atkinson et al., 2013; Callaghan et al., 2019; Gee et al., 2013; Hostinar et al., 2015; Tottenham et al., 2019). Early relational health is a powerful buffer against children’s stress. Parental buffering, where a caregiver’s presence regulates a child’s physiological response to threat, can reduce amygdala reactivity, a region of the brain central to fear and threat processing (Tottenham et al., 2019). Over time, this parental regulation is internalized by the child, contributing to resilience and psychological health (e.g., reduced anxiety; Callaghan et

al., 2019). These findings point to the importance of system-level supports that can create the conditions and environments for supportive caregiving; see Chapters 3, 4, and 5.

Buffering Effects on Stress Biology and Physical Health

There is a growing body of research showing that early relational health buffers the effects of global and specific stressors on children’s stress biology and physical health. Beginning with global stress indices, more positive parenting and less negative parenting buffered the effects of cumulative risk on epigenetic age acceleration in young children (Sullivan et al., 2023), and high maternal sensitivity buffered the effects of stress during early life and adolescence on physical health during midlife (Farrell et al., 2017).

With regard to specific stressors, several studies have shown that early relational health can serve as a protective factor in the face of poverty, financial strain, and/or low socioeconomic status. For example, in early childhood, more positive parenting buffered cortisol reactivity in response to stress among young children living in poverty (Brown et al., 2020); attachment to a caregiver moderated the association between income and cortisol levels during a well-child visit among toddlers (Johnson et al., 2018), such that among children living at or near poverty, children with secure attachments had lower cortisol levels than children with insecure attachments (this pattern was not found for children in families with higher incomes). These effects extend later in development as well. Secure mother–infant attachment at 15 months buffered the association between exposure to economic hardship during the first 5 years of life and earlier menarche (Sung et al., 2016). And maternal nurturance during childhood buffered the effects of low childhood socioeconomic status on metabolic syndrome components among midlife adults (Miller et al., 2011). Additionally, among adults who had low socioeconomic status during the first 5 years of life, those who reported growing up with high maternal warmth in childhood showed reduced proinflammatory signaling in adulthood relative to those who experienced low maternal warmth (Chen et al., 2011), consistent with a buffering pattern (though moderation analyses were not conducted).

Early relational health has been shown to reduce the effects of parental adverse childhood experiences on children. Specifically, parents’ observed emotional availability buffered the association between their adverse childhood experiences and their toddler’s hair cortisol concentration (Senehi et al., 2025). Similarly, parent–child relationship quality buffered the association between mothers’ adverse childhood experiences and their toddlers’ stress physiology (Gray et al., 2025). Similar buffering effects have been found with regard to parents’ mental health difficulties and intimate partner violence exposure. For example, infants’ attachment security buffered the

association between maternal depressive symptoms and the infant’s salivary inflammation, controlling for socioeconomic disadvantage and familial stress (Measelle & Ablow, 2018). And maternal sensitivity at infant age 7 months buffered the association between children’s exposure to intimate partner violence and increased cortisol reactivity at 24 months (Hibel et al., 2011).

Buffering Effects on Children’s Psychosocial Functioning

As with the literature examining buffering effects on stress biology and physical health, the growing body of research examining buffering effects on children’s psychosocial functioning spans different stressors and indicators. However, similar patterns have emerged. In one study, secure attachment to the caregiver at age 15 months reduced the association between being raised in poverty from ages 1–54 months and risk-taking at age 15 years (Delker et al., 2018). Several studies have examined how early relational health can buffer the association between parents’ adverse childhood experiences, mental health difficulties, and stress. For example, in one study of young children in an American Indian community, parents’ emotional availability statistically buffered the effects of parents’ adverse childhood experiences on children’s social-emotional functioning (Wurster et al., 2020). With regard to mental health difficulties, mothers’ responsive parenting buffered the association between their post-traumatic stress symptoms and their preschoolers’ disruptive behavior and stress-related symptoms (Greene et al., 2020). Similarly, sensitive fathering reduced the effects of chronic maternal depression on children’s psychiatric diagnosis at age 6 years (Vakrat et al., 2018). A composite measure of observed parenting behaviors, such as sensitivity, scaffolding, and supportiveness at child age 2 and 3 years, also buffered the effects of mothers’ prenatal life stressors on their 4- to 6-year-old children’s executive functioning and externalizing problems, controlling for household income, maternal IQ, and maternal postpartum and concurrent depression (Ahmad et al., 2022).

Although children’s relationships with their parents or caregivers have been the most widely studied, positive relationships with other adults may serve as a significant buffer as well. For example, in one study, high levels of grandmother involvement buffered preschool children from the association between certain observed maternal parenting behaviors and child externalizing behaviors (Barnett et al., 2010), controlling for the effects of child negative reactivity and family income-to-needs ratio. Similarly, high levels of maternal family support buffered the association between maternal adverse childhood experiences on their preschooler’s externalizing behavior problems (Hatch et al., 2020), controlling for maternal depression and children’s exposure to violence. Secure relationships to other caregivers such as

early childhood educators have also been theorized to serve as protective factors in the face of stressors such as trauma (Sciaraffa et al., 2018).

EARLY RELATIONAL HEALTH AND POSITIVE CHILDHOOD EXPERIENCES

As described above, much more is known about adverse childhood experiences and toxic stress than about positive childhood experiences and early relational health. This may simply reflect the fact that adverse childhood experiences and toxic stress are products of a biomedical approach to childhood adversity. At a fundamental level, the biomedical model is primarily interested in disease: the side of the wellness spectrum that runs from “disease” to “the absence of disease.” It is also primarily concerned with “diseases of life” and not “diseases of living,” the latter being conditions related to the broader context and not strictly biological. Simply put, the traditional biomedical model is disease oriented and primarily asks, “What is wrong with you?” It is therefore reactive rather than preventive, and it is reductionistic rather than contextual (see, e.g., Garner & Saul, 2025).

The biopsychosocial model of health expands the wellness continuum from the “absence of disease” to include varying degrees of wellness or flourishing. It is therefore more prevention oriented because it acknowledges that strengths might buffer disease or illness when it occurs. The biopsychosocial model of health is also more contextual, acknowledging that the broader psychosocial milieu also influences the disease process.

The recent advances in developmental science described briefly above (e.g., epigenetics, developmental neuroscience) build on the biopsychosocial model, add the element of time, and suggest an ecobiodevelopmental model. The early childhood ecology—including the physical, nutritional, relational, cultural, and environmental milieu—becomes biologically embedded through processes such as epigenetics and developmental neuroscience. The ultimate output of this biology is behavior, which in turn influences the developmental milieu. The dynamic dance between ecology and biology leads to changes at the molecular (e.g., DNA methylation), cellular (e.g., brain connectivity), and behavioral (e.g., behavioral allostasis) levels (Garner, 2016).

In sum, more is known about adverse childhood experiences and toxic stress because the biomedical model has been aptly applied to the issue of childhood adversity and yielded insights into how development might go awry in negative contexts, all the way down to changes at the molecular level. This view, however, belies the fact that all the known toxic stress–induced changes were in response to the child’s interactions with the broader developmental milieu. The ecobiodevelopmental model of disease and wellness acknowledges that the ecology—the context in which child development occurs—interacts with our biology to influence outcomes across the

life course (Garner, 2016). The ecobiodevelopmental model of disease and wellness encourages consideration of how to get things right the first time (Garner & Saul, 2025).

Expanding Understanding of Positive Childhood Experiences

Consistent with this perspective, research on positive childhood experiences as counterparts to childhood adversity has grown in recent years. Such research seeks to understand how positive childhood experiences become embedded and influence life course trajectories positively. It asks the following: Do positive childhood experiences simply buffer adverse childhood experiences, making adverse childhood experiences less “toxic,” or are positive childhood experiences biologically necessary for development? And perhaps more fundamentally, how are positive childhood experiences defined? Box 2-2 summarizes some of the scales that have been used to date. Each of these measures has been shown to be associated with positive developmental outcomes even in the presence of adversity.

Generally, positive childhood experiences include relational elements such as emotional safety with caregivers, continuity in supportive relationships, community traditions, and a sense of belonging. Research indicates numerous ways that positive childhood experiences are correlated with improved health and well-being. Several studies have found that children experiencing positive childhood experiences, such as attuned and responsive caregivers, ample opportunities for developmentally appropriate play and reading aloud, and participation in programs such as Reach Out and Read and PlayReadVIP, are more likely to have healthy lifestyles, academic success, and economic stability decades later (Bethell, Gombojav, & Whitaker, 2019; Bethell, Jones, et al., 2019; Jimenez et al., 2024; Sege, 2024; Szumlas et al., 2021; Willis et al., 2007; Yogman et al., 2018). Linkenbach and Ritz (2025) summarized the following for the committee:

• Positive childhood experiences are predictive of lower rates of depression, anxiety, and social isolation in adulthood—even among individuals with significant adversity (Bethell, Jones, et al., 2019).
• Positive childhood experiences are associated with reduced likelihood of adult smoking and high-risk alcohol use (Graupensperger et al., 2023).
• Positive childhood experiences serve as protective factors for mental health in pandemic-era youth with adverse childhood experiences (Samji et al., 2024).
• Positive childhood experiences are associated with both reduced internalizing and externalizing symptoms and reduced odds of scoring in the clinical range in anxiety, depression, somatization,

of Children’s Health, studies have measured the health risks, social health risks, and relational health risks and their influences on the early and lifelong health of children and the adults they become. A recent population-based study using the Integrated Child Risk Index demonstrates that even without social health risks,⁴ children exposed to two or more relational health risks⁵ are 2.18 times more likely to have medical health risks⁶ compared with those not experiencing relational health risk (Bethell, Blackwell, et al., 2022). Over half (50.8%) of children with medical health risks experience evidence-based relational health risk (Bethell, Blackwell, et al., 2022). This and related studies also show the powerful mitigating role of family resilience and connection on child flourishing and school readiness/engagement even amid adverse childhood experiences (Bethell et al., 2014, 2016; Bethell, Garner, et al., 2022; Bethell, Gombojav, & Whitaker, 2019; Bethell, Jones, et al., 2019). Furthermore, this body of research suggests that the absence of family resilience and connection and positive childhood experiences is independently associated with poorer child flourishing and school readiness/engagement and with greater child and adult mental and physical health problems (Bethell, Gombojav, & Whitaker, 2019; Bethell, Jones, et al., 2019). Families describe positive relational experiences based on family resilience, connection, and positive childhood experiences as promoting flourishing and well-being (Bethell, Gombojav, & Whitaker, 2019; Bethell, Jones, et al., 2019). All children, but particularly children who experience adversity, need positive childhood experiences to thrive and flourish. These appear to influence life course trajectories by promoting early relational health.

CONCLUSION

Early relational health benefits every child, family, and community, shaping pathways for health and well-being across the life course. It develops over time through small moments of connection, such as reading aloud, and occurs anywhere children spend time. It is associated with positive psychological, social, and physical health outcomes and can serve as a protective factor that buffers against the adverse effects of stressors, challenges, and adversities. The committee’s review points to the following conclusions about the impact of early relational health:

• A large and robust evidence base provides clear evidence for linkages between early relational health and children’s short- and

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⁴ For example, economic hardship, food/housing insecurity, unsafe neighborhoods.

⁵ For example, two or more adverse childhood experiences, poor parental coping.

⁶ For example, multiple chronic physical/mental health conditions, functional limitations.

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