The Neurodevelopmental Impact of Stress, Adversity, and Trauma:

Implications for Social Work
(part 1)

Janet R. Shapiro and Jeffrey S. Applegate

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Excerpted from Neurobiology for Clinical Social Work, Second Edition© 2018 by Janet R. Shapiro and Jeffrey S. Applegate. The following is from Chapter 5: “The Neurodevelopmental Impact of Stress, Adversity, and Trauma: Implications for Social Work.” Used with the permission of the publisher, W. W. Norton & Company.

One of the most widely recognized applications of neuroscience as it pertains to clinical social work is our enhanced understanding of how early adversity, trauma, and toxic stress can negatively impact neurodevelopment and, in turn, health and mental health across the life span (Garland & Howard, 2009; Kaufman & Charney, 2001; National Scientific Council on the Developing Child, 2014; Shonkoff et al., 2009). For social workers interested in understanding mechanisms of risk and resiliency, it is important to ask the question, how does exposure to early adversity and stress precipitate neurodevelopmental changes that, in turn, are associated with increased risk behaviors and poor health outcomes? The answer to this question requires multidisciplinary awareness of research from fields such as epidemiology, developmental psychopathology, neuroscience, and, in particular, brain development in early life.

Practitioners who work with young children and their families know that a high percentage of young children are experiencing stress associated with poverty, child abuse and neglect, and separation from caregivers due to factors such as incarceration and substance abuse. The research we review in this chapter shows that these types of early experiences, particularly in the absence of supportive care, can set children on a trajectory of disrupted neurodevelopment and risks to psychosocial and health outcomes. Thus, children in particular social contexts (e.g., economically vulnerable families) face not only the challenges of income inequality in a direct sense but are also at increased risk for poor health outcomes, contributing to social disparities in health (Green & Darity, 2010; Jones Harden, Buhler, & Jiminez Parra, 2016).

For social work practitioners interested in the impact of stress on the developing brain, two areas of research are particularly important. First, the Adverse Childhood Experiences (ACE) studies demonstrate, from an epidemiological perspective, the connection between specific types of early adversity and developmental and health outcomes across time. Relatedly, research describes how long-term activation of the stress response system can create neurodevelopmental and neuroendocrine changes that link unmediated stress to health outcomes in particular ways (Gunnar, 1998, 2000; Hart, Gunnar, & Cicchetti, 1996).

This chapter begins with a brief overview of the ACE studies, a set of ground-breaking, epidemiological studies that demonstrated the connection between childhood stress and adversity, and risk for poor health outcomes later in life. Key to understanding this trajectory is an awareness of how stress and adversity precipitate neurodevelopmental and neuroendocrine changes, particularly during sensitive periods of brain development. For this reason, this chapter also provides an overview of the stress response system and research on the impact of unmediated stress on the developing brain and nervous system. Finally, and from a more hopeful point of view, research on early adversity shows that supportive and secure attachment experiences are important buffers against stress exposure in early childhood (National Scientific Council on the Developing Child, 2007). For this reason, it is vitally important that we understand more about what happens when conditions exist that interfere with the caregiver’s ability to provide attuned and responsive care (Perry, Ettinger, Mendelson, & Le, 2010). We briefly consider the issues of maternal depression and parental substance use from this perspective.

THE ACE STUDIES
The ACE studies are multidisciplinary publications that originally stemmed from an epidemiological study undertaken as a collaboration between the Centers for Disease Control and researchers from Kaiser Permanente (Felitti, 2009; Felitti et al., 1998). Based on a 10-item questionnaire that asked adults to retrospectively endorse whether they had experienced specific adverse events as a child, subjects were assigned an ACE score, which represented the number of adverse events endorsed. These events included experiences familiar to clinical social workers who work with vulnerable children, adults, and families and include abuse and neglect; witnessing intimate partner violence; having a parent who abused drugs, had a mental illness, or was incarcerated; and experiencing separation from a parent or primary caregiver. The strongest finding of the early ACE studies was that the higher an individual’s ACE score, the more likely he or she was to experience a host of negative health outcomes as an adult, even when other sociodemographic factors were controlled for in data analyses (Dube, Felitti, Dong, Giles, & Anda, 2003).

The ACE pyramid, depicts a trajectory, moving forward in time, that connects early experiences of adversity to neuro-developmental impacts, which in turn are associated with health risk behaviors, early onset of negative health outcomes, and, ultimately, mortality rates (Shonkoff et al., 2012). Specific associations have been documented between higher ACE scores and increased likelihood of neurodevelopmental alterations in areas such as memory (Brown et al., 2007), the emergence of depression and depressed affect (Chapman, Anda, Felitti, Dube, Edwards & Whitfield, 2004), health risk behaviors such as alcohol use and smoking (Dube et al., 2003), and the emergence of chronic disease such as autoimmune diseases and cancer (Brown, Thacker, & Cohen, 2014).

From a social work perspective, research on ACE points to the importance of primary prevention and protecting the developing child from exposure to toxic stress, as well as to the importance of intervention at various points along the ACE pyramid trajectory. The American Academy of Pediatrics argues that research on the connection between early adversity and later health disparities should be integrated with current work in neuroscience and neurodevelopment to create a holistic approach to prevention and intervention. The academy suggests that “research in molecular biology, genomics, immunology, and neuroscience” must be integrated into our understanding of the processes by which early experiences shape later outcomes in order to inform “science-based strategies to build foundations for children’s lifelong health” (Johnson et al., 2011, p. 319). In particular, these researchers point to the quality of early caregiving relationships as key to emerging neuroendocrine, neurobiological, and other body systems that build the foundation for lifelong health (National Scientific Council on the Developing Child, 2007).

THE STRESS RESPONSE SYSTEM
Most clinicians are aware that even age-related changes, normative in nature, create stress of a certain sort for the developing person. A key focus of assessment is often the differentiation of short-term difficulties, perhaps understood as stress reactions to maturational demands, from longer-term, more persistent concerns or exposure to acute or overwhelming stressors that may give rise to serious developmental and mental health vulnerabilities (Boyd-Webb, 2015; Davies, 2010). Embedded in this understanding is the notion that not all stress has long-lasting negative impact and that for development to move forward, some exposure to stress may be necessary and developmentally optimal. Thus, researchers have differentiated among types of stress (Shonkoff & Phillips, 2000).

In a working paper titled, “Excessive Stress Disrupts the Architecture of the Developing Brain” (National Scientific Council on the Developing Child, 2014), experiences of stress are divided into three categories associated with differential activation of the stress response system. Positive stress is described as short lived in nature, moderate in intensity, and associated with an adaptive and brief activation of stress response systems followed by a timeline return to homeostasis, or baseline. These are the types of stressors that often accompany developmental transitions, such as starting school. With good-enough adult support, the developing child learns to negotiate new maturational tasks and potentially gains a sense of mastery and optimism. At the same time, an event that is manageable to one child may be in a different category for a child carrying preexisting vulnerabilities and experiences of traumatic stress. For a child who has experienced repeated attachment disruptions and lack of access to empathic care, the same event—starting at a new school—may be much more fraught. And, so an example of positive stress can become, for any given individual, more challenging. Tolerable stress refers to those stressors that are significant enough to potentially have longer-term neurobiological and neuroendocrine impacts if not offset by the provision of contingently responsive and empathically attuned support. These types of stressors, depending on the age of the child, will likely require adult intervention to reestablish a sense of homeostatic balance. For this level of stress, children will likely need attuned intervention provided by adults who have some insight into how moderately sustained activation of their stress response system may impact their physiology, behavior, cognition, affect, and even sense of identity. Toxic or traumatic stress refers to intense and sometimes frequent exposure to overwhelming stressors in the absence of supportive and responsive adult care. When children are exposed to toxic or traumatic stress, their stress response systems are activated and remain activated over long periods of time, potentially even after the stressor has been removed. This type of stress has the greatest potential to have negative impacts on the developing brain, such as (1) the volume of different parts of the brain, (2) neuroendocrine changes that may increase individuals’ susceptibility to future stressors by increasing their overall level of reactivity to stress exposure, and (3) related impacts on development in multiple spheres, including growth and wellness, cognition and executive functioning, and indexes of emotional well-being and mental health (Loman & Gunnar, 2010; Lupien et al., 2009; Lupien, King, Meaney, & McEwen, 2001; McEwen, 2008; Shonkoff et al., 2009).

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