Childhood Trauma and Toxic Stress

Early Childhood and Brain Architecture: Serve and Return

Brain development begins right after conception and continues through birth, childhood, adolescence and into early adulthood. Neuroscientists use the term “brain architecture” to illustrate the idea that brains are built over time in a predictable sequence, with basic circuits and skills forming a foundation for the more complex circuits and skills that follow. This foundation is built through our early years by positive experiences and responsive relationships.1

Just like building a new home, certain parts of the developing brain are built in a particular order. What is built early (the foundation) must be strong enough to support the long-term structure.

The quality of the child-caregiver relationship has significant and enduring effects on brain development. Stable, responsive, nurturing relationships between children and the adults in their lives provide positive experiences that build the architecture of the developing brain in beneficial ways. Without these relationships, children do not have the same opportunity to practice cognitive, social, and emotional skills, and the development of these brain circuits may be compromised.2

Serve and Return

This is the term that describes the “back-and-forth” exchange between a child and an attuned adult. When an infant or young child babbles, gestures, or cries, and an adult responds appropriately with eye contact, words, or a hug, neural connections are built and strengthened in the child’s brain that support the development of communication and social skills.3

Attachment and Relationships

The study of parental influence on young children’s development has been explored through viewing the results of various forms of parent-infant bonding in Attachment Theory.4 This is a rich area of research that includes many variations but for our purposes, we will focus on two broad forms of attachment, secure and insecure.

Secure attachment occurs when a caregiver is attentive to the needs of the baby. The parent recognizes the baby signals of hunger and other simple biological needs but also responds to emotional signals from the baby for attention, a cuddle or soothing after an upset, like falling down when learning to walk. It’s not necessary that every need be met, but that most of the time the baby has a growing sense that if she needs help, help will come.

Over the course of childhood this security allows the developing brain to build good connections between the prefrontal cortex (reasoning part of the brain) with the mid-brain structures; (which are involved in sensing emotions and their regulation, encoding of memory, achieving body awareness, and developing empathy). With secure attachments, the growing child is “wired” for safety; has a felt sense of worthiness, love, and security.

Insecure attachment is characterized by caregiver neglect and/or outright abuse which then undermines normal brain development so much so that the child’s ability to regulate emotion, have a sense of their own body, and trust in the good will of others is seriously impaired.

A child with an insecure attachment history has a blueprint of relationships that may mix up the need for love and connection with feelings of fear and unease. So that in adulthood a person may find that abusive, dangerous or dismissing relationships seem predictable and normal. In this case, the growing child is “wired” for fear, and has a felt sense of insecurity.

Rather than blame parents and caregivers, a trauma-informed perspective recognizes that attachment styles are often repeated across generations:

It is very much the case that no one sets out to harm their child. Most people want to be good, responsive caregivers, however a history of neglect and abuse in a person’s past, without support for change, makes it more likely that they will have difficulty being attuned to their children. Young families struggling with poverty, unsafe housing and few job prospects will face extra demands that make it difficult to be fully present with their children.5

JC Baer, 2012

Understanding the interconnectedness between relationships, the brain and the mind is important because it can help promote relationship by helping to identify qualities that will allow clients to feel heard and seen as well as promote recovery and well-being.

Toxic Stress

Everyone experiences stress, and all children must learn to cope with it as a healthy part of normal development. Positive stress, which is manageable and minor, helps children strengthen their executive function skills. A supportive caregiver can help a child navigate even intensely stressful experiences. However, when stress is extreme, prolonged, and unmitigated by supportive relationships, such as in an abusive, chaotic, or neglectful environment, it weakens brain architecture and can disrupt healthy development. Children who experience intense, ongoing stress – which scientists call toxic stress – tend to have lower executive function capabilities and are at higher risk for lifelong physical and mental health problems.6

Three types of Stress Responses

The Centre on the Developing Child at Harvard University stresses that it is important to distinguish among three kinds of responses to stress: positive, tolerable, and toxic. As described below, these three terms refer to the stress response systems’ effects on the body, not to the stressful event or experience itself:[7]

Positive stress response is a normal and essential part of healthy development, characterized by brief increases in heart rate and mild elevations in hormone levels. Some situations that might trigger a positive stress response are the first day with a new caregiver or receiving an injected immunization.

Tolerable stress response activates the body’s alert systems to a greater degree as a result of more severe, longer-lasting difficulties, such as the loss of a loved one, a natural disaster, or a frightening injury. If the activation is time-limited and buffered by relationships with adults who help the child adapt, the brain and other organs recover from what might otherwise be damaging effects. Ultimately, tolerable stress can help to build positive coping strategies and resilience to subsequent stress when support is available from adults.

Toxic stress response can occur when a child experiences strong, frequent, and/or prolonged adversity—such as physical or emotional abuse, chronic neglect, caregiver substance abuse or mental illness, exposure to violence, and/or the accumulated burdens of family economic hardship—without adequate adult support. This kind of prolonged activation of the stress response systems can disrupt the development of brain architecture and other organ systems, and increase the risk for stress-related disease and cognitive impairment, well into the adult years.


The term “Adverse Childhood Experiences” or “ACEs” comes from the 1998 study led by Dr. Vincent Felitti[8] in partnership with the US Centers for Disease Control and Prevention (CDC) and Kaiser Permanente one of the largest Health Maintenance Organizations (HMO) in the US.  The study examined exposure to childhood adversity, including abuse and neglect, and “household dysfunction” like domestic violence, parental mental illness, or parental substance abuse. Researchers assigned an “ACE score” to each participant by adding up the number of adversities the participant reported.

Important findings include:

  • 79% of participants had at least one ACE
  • 12.6% had more than 4
  • There is a dose-response relationship between ACEs and health outcomes; the more ACEs a person scores, the higher the risk for negative health outcomes.
  • Even when a person with ACEs does not engage in any high risk behaviour, they are still more likely to develop issues such as heart disease or cancer.
  • Challenges that children face in school, in their health, and other aspects of life are often the symptoms of ACEs and toxic stress. The good news is, the earlier we can identify that a child is experiencing ACEs and toxic stress, the sooner children and families can be connected to the services they need.
  • Children are especially sensitive to this the stress activation because their brains and bodies are still developing. High doses of adversity not only affect brain structure and function, they affect the developing immune system, developing hormonal systems, and even the way our DNA is read and transcribed.[9]

Current systems such as health, justice, human services, and education bear the brunt of the burden produced by ACEs, yet are often poorly equipped to recognize and respond to children and adults suffering from the cumulative effects of childhood trauma. Recognizing the high prevalence and broad impact of ACEs on a number of different outcomes is the first step in creating more trauma-informed systems and services. For more information on trauma-informed care, visit here

Preventing Childhood Toxic Stress

Supportive adult relationships can help buffer children against the damaging effects of stress by helping them calm down, feel safe and secure, problem-solve, and practice coping skills. The earlier and more frequently buffering occurs, the better the outcome for the child. When ongoing adversity cannot be prevented, children need adult support to buffer its effects so that stress becomes tolerable and not toxic to development. Protective interventions help to buffer the effects of adverse experiences by building the foundations of resilience in children.[10]

The single most common factor for children who develop resilience is at least one stable and committed relationship with a supportive parent, caregiver, or other adult[11]

Organizational responses to childhood toxic stress:

To be maximally effective, policies and services should[12]:

  1. Support responsive relationships for children and adults.
  2. Strengthen core life skills.
  3. Reduce sources of stress in the lives of children and families.

These three principles do not operate in isolation. In fact, they are highly interconnected and reinforce each other in multiple ways. For example, helping parents and caregivers improve their stress responses supports their ability to engage in serve-and-return interactions with the children in their care and to create a more stable and predictable care-giving environment.

When neglected and maltreated children grow up to become parents, they are at significantly higher risk of perpetuating the cycle of neglect and maltreatment. By adopting a two-generation approach and delivering interventions to both caregivers and children in the context of the care-giving relationship, new interventions are able to disrupt intergenerational cycles of neglect and maltreatment, and continue to support healthy development long after the intervention ends.


Siegel, Daniel J., and P. H. D. Tina Payne Bryson. 2012. The WholeBrain Child. New York, NY: Random House

Perry, B. D., & Szalavitz, M. 2007. The boy who was raised as a dog. Basic Books.

[1] Alberta Wellness Brainstory Certification

[2] Alberta Wellness Brainstory Certification

[3] Harvard Centre of Developing Child

[4] Bowlby, John (1988)

[5] JC Baer, 2012

[6] Alberta Wellness Brainstory Certification

[7] Centre of the Developing Child at Harvard – Key Concept: Resilience

[8] Centers for Disease Control and Prevention, National Center for Injury Prevention and Control, Division of Violence Prevention. December 27, 2015.

[9] Nadine Burke Harris – How childhood trauma effects health across a lifetime, retrieved from

[10] Alberta Wellness Brainstory Certification

[11] Centre of the Developing Child at Harvard – Key Concept: Resilience

[12] Alberta Wellness Brainstory Certification