Stress has been intertwined into the lives of people from birth onward. Research has found considerable amounts of evidence that early life stress impacts the body and extends into adulthood (Alexe, Syridou, & Petridou, 2006; Entringer et al., 2012; Juster, Mcewen, & Lupien, 2010; Vaiserman, 2011). Stress is the body’s response to an activation of the hypothalamic-pituitary-adrenomedullary system which results in increases in the stress hormones, for example cortisol, norepinephrine, adrenaline and corticotrophin-releasing hormone (CRH) (Shonkoff, 2012). The body’s response system activates to deal with stress and how it will deal the activation stimuli (Center on the Developing Child, 2017; Shonkoff, 2012). Traditionally, stress was thought to be determined or influenced by genetic predispositions however more recent research has suggested that previous experiences play a crucial role (Garner, 2013; Ouellet-Morin et al., 2008). Stress reactivity, similar to brain development, results from the complex interaction between genes and the environment over time (Garner, 2013).
Within the body, the hypothalamic-pituitary-adrenal (HPA) axis is the major stress response system that sends out stress hormones and is responsible for helping the body adapt and maintain stability during stressful situations (Heim, Newport, Mletzko, Miller, & Nemeroff, 2008). Early experiences of stress in the womb as well as postnatal experiences can impact the stress responsiveness of the child (Shonkoff, 2012). Research has found that maternal nutrition and maternal functioning and maternal diseases (e.g. gestational diabetes can influence a baby’s hormones (e.g. Leptin) which help the baby adapt to postnatal life as well as influences the stress responses and growth rates of a baby and are key risk factors for toxic stress (Alexe, Syridou, & Petridou, 2006; Johnson, Riley, Granger, & Riis, 2013). Early experiences such as maternal stress within the womb, malnutrition, maltreatment, neglect, and other adverse experiences can negatively impact a child’s growth and ability to adapt and handle stress.
Research has found that repeated adverse experiences that occur early in a child’s life can alter the development of neural circuits, increase stress responsiveness which in turn can set a lower threshold for future responses to stress, changes in emotional regulation, and lead to negative outcomes later in life, as increase the likelihood of chronic diseases including, autoimmune disorders, and increase risk for obesity and asthma (Bartholomeusz, Callister, & Hodgson, 2013; Entringer et al., 2012; Garner, 2013; Shonkoff, 2010; 2012).
Literature on stress has identified three form of stress: positive, tolerable, and toxic. The first form of stress is positive stress. Positive stress is short-lived stress that increases heart rate and blood pressure and is healthy when it is experienced within the context of supportive relationships and environments which help bring the body’s stress response (cortisol levels) back to its normal baseline (Garner, 2013; Shonkoff, Boyce, & Mcewen, 2009; Shonkoff, 2010). Examples of positive stress are normative experiences such as receiving a shot, taking an exam, or frustration from being stuck in traffic (Shonkoff et al., 2009). Positive stress is an important part of healthy development and can motivate change and can build resilience (Garner, 2013; Shonkoff et al., 2009).
Another form of stress is tolerable stress. Tolerable stress is a physiological state that could potentially disrupt brain development but it still buffered by relationships that are supportive and help bring about adaptive coping and lasts longer than positive stress (Garner, 2013; Shonkoff, 2010). Examples of tolerable stress would be the death or illness of a loved one, a natural disaster (tornado, hurricane, etc.), or losing one’s home (Shonkoff et al., 2009). Tolerable stress occurs within a time-limited period and has supportive relationships that help the body recover from any negative impacts (Shonkoff et al., 2009).
The last form of stress found in literature is toxic stress. Toxic stress is strong, frequent activation of the body’s stress responses and the stress responses remain elevated for long periods of time and leads to the body being in a constant state of responding to it (Center on the Developing Child, 2017; McEwen & McEwen, 2017; Shonkoff et al., 2009). Toxic stress lacks the buffering support relationships that the other two forms have (Shonkoff, 2009, 2010). Some examples of toxic stress include recurring physical or emotional abuse, parental substance abuse, chronic neglect, extreme poverty, and severe maternal depression (Shonkoff et al., 2009). Toxic stress disrupts brain development, leads to lower stress management thresholds, and affects other organs within the body increasing the body’s risk of disease in the adult years (Shonkoff et al., 2009). Early experiences of toxic stress or other negative experience have been found to inhibit the development of children (Perry et al., 1995; Shonkoff, 2010; 2012).
Impact of Toxic Stress. Research has found that toxic stress alters the body’s functioning (Garner, 2013). Toxic stress impairs the brains ability to function effectively and the body remains in a constant state of survival mode and become hyper-responsive as well as it can increase the risk of stress related disorders or disease into the adult years of life (Center on the Developing Child, 2017; Garner, 2013; Perry et al., 1995; Shonkoff, 2010). Toxic stress body alters to deal with toxic stress, and becomes hyper-responsive or (Garner, 2013). The National Scientific Council on the Developing Child (2010) has found that early exposure to toxic stress affects children’s ability to learn and development. Toxic stress and elevated levels of cortisol can inhibit the development of neurons in the hippocampus, which has been found to be involved in the encoding of memory as well as other functions. Also, toxic stress constrains the hippocampus’s ability to promote contextual learning, which in turn makes it difficult to distinguish dangerous vs safe conditions (Shonkoff, 2012).
When a child has early experiences that are threatening, full of neglect, uncertainty, and abuse, the stress management systems are overactive which can involve disruptions between brain circuitry development and establishes a “short fuse” for the body’s stress response (Shonkoff, 2010). Toxic stress has been linked to depression, diabetes, incarceration, school failure, divorce, and cause alterations within the immune system (Garner, 2013; Luby, Heffelfinger, Mrakotsky, & Brown, 2003). Research has found that stress cortisol reactivity is linked to depression in preschool children (Luby et al., 2003). Luby et al., (2003) conducted a study to investigate APA axis reactivity in young children who had been diagnosed with a clinical depression syndrome. The results provided support that alterations in the HPA axis can lead to the developmental neurobiology of major depressive disorder (MDD) (Luby et al., 2003). Individuals with MDD and posttraumatic stress disorder (PTSD) has also been found to have alterations or abnormalities of the hippocampal structure suggesting that a small or abnormal hippocampus is a risk marker (Bremner, Narayan, Anderson, & Staib, 2000; Frodl et al., 2002; Heim et al., 2008).
Toxic stress in early childhood can sometimes develop further into a disorder. Toxic stress can manifest itself in a variety of disorders including: Posttraumatic stress, adjustment disorder, reactive attachment disorder, and disinhibited social engagement. In order for an individual’s stress to move to or be categorized as a disorder it must have the following criteria: “causes distress to the infant/young child, interfere with the infant’s/young child’s relationships, limit the infant’s/young child’s participation in developmentally expected activities or routines, limits the family’s participation in everyday activities and routines, and limit a child’s ability to learn and develop new skills or interfere with the developmental process (Zero to Three, p. 116, 2016). The following sections will focus on research and criteria specifically related to the posttraumatic stress disorder in young children.
Posttraumatic Stress Disorder. Posttraumatic stress disorder (PTSD) is a specific stress responses to a traumatic event or exposure to trauma including neglect, family violence, physical or sexual abuse, painful or frightening medical procedures, car accidents, or events similar (Zero to Three, 2016). In order for infants or young children to be diagnosed with PTSD, they must experience the trauma directly, witness it, or be told of about trauma that impacted a significant individual in their life (Zero to Three, 2016). PTSD can manifest itself in children differently, for some it may reduce their responsiveness and cause the child to withdrawal while for others it manifests itself as a reoccurring fear (Zero to Three, 2016). In the DC 0-5, the following conditions must be present to be classified for PTSD: child displays evidence that they are experiencing the trauma (nightmares, reenactments of event, repeated questions about trauma, and major distress at reminders of trauma, dissociative episodes, and physiological reactions), tries to avoid anything that reminds them of the trauma, lack of positive emotions (social withdrawal, sadness, reduce interest, and reducing of positive emotions), shows increases in arousal (trouble sleeping, hypervigilance, and heightened levels of irritability), and the symptoms of PTSD continuously interferes with the functioning of child and family (Zero to Three, 2016).
The mentioned criteria for PTSD must be present in a child for one month or more following trauma (Zero to Three, 2016). The diagnostic criteria for PTSD such as, difficulty concentrating, hypervigilance, agitated breathing, repeated experiences of the trauma (e.g. flash backs, nightmares, or preoccupation with the traumatic even), and avoidance (e.g. social withdrawal, sadness, and/or lack of positive expression), indicates disruptions in a child’s emotional, physiological and behavioral regulation systems (Bosquet Enlow, Egeland, Carlson, Blood, & Wright, 2014; Zero to Three, 2016).
Research on PTSD. Studies over PTSD have found considerable evidence that individuals who experience early childhood trauma such as neglect, physical and sexual abuse are more prone to have posttraumatic stress symptoms than individuals who did not experience trauma in their early years (Elliott & Briere, 1995; Epstein, Saunders, & Kilpatrick, 1997; Wolfe, Sas, Wekerle, 1994; Widom, 1999; Yehuda, Halligan, & Grossman, 2001). Literature over PTSD in young children have studied various traumas including, experiencing cancer, severe burns, and sexual trauma. Studies over each of these traumas have found that increased age of child at diagnosis and maternal PTSD is linked to higher risk of developing PTSD symptoms in a child (Graf, Bergstraesser, & Landolt, 2013); correlations between a child’s symptoms of PTSD and the trauma severity, indications of genetic vulnerability between parent and child to traumatic stress, as well as associations with the quality of the family and maternal PTSD symptoms to the child’s symptoms of PTSD (Graf, Schiestl, & Landolt, 2011; Saxe et al., 2005); memory recovering and affect regulation was linked to posttraumatic stress (Elliot & Briere, 1995).
Research over PTSD its development in individuals after a traumatic event has established a clear and significant link between parental PTSD and the child’s PTSD (Yehuda, Halligan, & Grossman, 2001). It is also clear that children who suffer from PTSD have difficulties emotionally and behaviorally. Various interventions have been developed to help both parent and child negate PTSD symptoms and address the emotionally and behaviorally problems that arise.
Risk Factors for PTSD. Research on PTSD has found there to be several risk factors for children to develop PTSD. One of those factors is the transmission of PTSD from parent to child (Bosquet et al., 2014). In a study looking at the transmission of trauma symptoms from parent to child as a result of severe intimate partner violence, the results indicated a significant association between maternal trauma symptoms and the child’s symptoms (Bogat, DeJonghe, Levendosky, Davidson, & Von Eye, 2006). Roberts et al., (2006) found that mother’s symptoms of PTSD predicted greater risk of PTSD symptoms occurring in children. Other research has found that infants whose caregiver experienced trauma due to a threat were more likely to be diagnosed with PTSD than the children of caregivers who did not survive the threat (Scheeringa, Zeanah, & Osofsky, 1995).
Attachment history has also been found to be a predictor of PTSD symptoms. Research has provided evidence for associations for maternal PTSD and insecure attachment between mother-child and increase risk of developing PTSD (Bosquet Enlow et al., 2014). Carlson (1998) found that a history of attachment disorganization can be linked to an increase of risk for psychological impairment and development of dissociative symptoms, which research has found to be a potential factor for PTSD symptoms, in children and can impact them into their and into the adult years. In a study by Gaenbauer (1982), a 3-month-old girl was repeatedly abused, starting as early as 2 weeks of age and displayed strong symptoms for PTSD, such as a loss of interest in activities, irritability, and hypervigilance. The girl’s father had been abusing her and as a result the girl had a hard time establishing secure attachments with men and displayed aversion to them but was able to not to women (Gaenbauer, 1982; Scheeringa, 2009).
Another potential risk factor for PTSD is low self-awareness or self-regulation. Studies have found that those who respond to trauma by dissociation and have increases in their emotional responses are at higher risk for developing symptoms of PTSD (Özdemir, Güzel Özdemir, Yilmaz, & Boysan, 2015; Ozer, Best, Lipsey, & Weiss, 2003; Putnam, 1995; Ursano et al., 1999). However, self-regulation abilities may also be a resilience factor for trauma. Maternal factors, attachment, and low self-regulation/dissociation are found within literature to be predictors of PTSD symptoms in children. These factors are important to remember when discussing the development of PTSD in young children and possible therapeutic approaches.