And my kids suffer too. From being born from me, they were raised by a woman who has gone through this… This is my brain… On Adoption…
Read it, and weep. Its time to change this shit around here.
Evidence for the effects of trauma on the brain
Studies that address the relationship between trauma and cognitive development generally take the form of either neuroimaging studies or neuropsychological studies. Neuroimaging studies focus on the growth of important brain structures, and on how efficiently the brain responds to emotional stimuli (e.g., a picture of an angry face). Studies in the field of neuropsychology use performance on well-established tasks to infer brain functioning, for example by measuring memory and attention span during defined tasks and make inferences about functioning and behaviour from these results (for reviews of neuroimaging and neuropsychological studies see McCrory et al., 2010; McCrory et al., 2011).
Collectively, this research suggests that the brain development of children in care is likely to be affected in some way by their early experiences. The neuropsychological impact of adversity can vary widely, however, and not all children that experience adversity go on to develop difficulties related to learning, memory and attention. The impact of adversity on brain development may depend on whether children primarily have experienced deprivation or threat during their pre-care life: resulting in either delayed cognitive development or dis-integration of cognitive skills, respectively (see McLaughlin et al., 2014).
This field of research is not well developed and is conceptually and methodologically underdeveloped. For instance, antenatal alcohol exposure frequently affects later cognitive functioning (see McLean & McDougall, 2014; McLean, McDougall, & Russell, 2014), but studies of children in care rarely report on history of antenatal alcohol exposure.
Nonetheless, there are some common findings from the research that are summarised in the following sections.
Stress hormone dysregulation
Trauma and adversity is commonly described as leading to a hyper-arousal of the hypothalamic-pituitary-adrenal axis (HPA axis) that results in changes in brain development. In reality, this is almost certainly an oversimplification of the relationship between trauma and the stress hormone system (Frodl & O’Keane, 2013; McCrory et al., 2011; McLaughlin et al., 2014). While there is consensus that early stress leads to an ongoing dysregulation of the body’s HPA axis stress response system (see McEwan, 2012), the exact nature of this dysregulation is debated (Frodle, & O’Keane, 2013; McCrory, De Brito, & Viding, 2010; Sapolsky et al, 1996). The research findings suggest that the stress response system can either become chronically over-activated or under-responsive over time (Frodl & O’Keane, 2013; McCrory et al., 2011; McEwan, 2012; McLaughlin et al., 2014) in response to a complex mix of factors (including chronicity and timing of abuse) that are currently unclear. Therefore, while the findings support the idea that childhood trauma is associated with a disruption in the HPA axis response, they do not uniformly support the idea of chronic hyper-activation, as is commonly assumed.
Although dysregulation of the stress response system is associated with changes in the development of key brain structures (e.g., hippocampus), the association is not as straightforward as is suggested by popular accounts (see Box 1). At present, the evidence in support of the link comes mainly from studies of adults that retrospectively report a history of abuse, rather than from studies of children, meaning that other influences cannot be discounted.
The precise relationship between timing and nature of adversity, HPA axis dysregulation and impaired brain development is unclear, and can only be determined by ongoing longitudinal research (McCrory, et al., 2011).
Changes in brain structure and functioning
Most brain imaging studies investigating the relationship between trauma and changes in the development, regulation and responsiveness of a child’s brain over time are based on studies of adults who report a history of childhood abuse, rather than on studies that track children’s development over time (McLaughlin et al., 2014; Teicher, Anderson, & Polcari, 2012).
In contrast, neuropsychological studies generally provide solid evidence for a link between trauma and brain function. Neuropsychological studies are more useful than neuroimaging studies in assessing children’s everyday functioning because they provide us with more direct insight into the difficulties that children experience. On the whole, neuropsychological studies tend to show that children who have experienced or witnessed violence, trauma, abuse or neglect do experience cognitive difficulties in one or more areas, when compared to children who haven’t experienced these adversities (McCrory et al., 2011; McLaughlin et al., 2014). Some of the main cognitive difficulties are summarised in the following sections.
General cognitive and language delay
On the whole, children exposed to neglect may be more vulnerable to general delays in cognitive and language development (De Bellis et al., 2009; Hart & Rubia, 2012; McLaughlin et al., 2014). Neglected children and those raised in poverty may be more at risk of general cognitive delay than those exposed to abuse (Hilyard & Wolfe, 2002; McLaughlin et al., 2014).
Among abused children, increasing severity of abuse is associated with lowered IQ relative to matched controls (Carrey et al., 1995; Hart & Rubia, 2012; Prasad, Kramer, & Ewing Cobbs, 2005; Pollak et al., 2010). These studies don’t generally control for other factors that can affect IQ scores, such as education level and presence of post-traumatic stress disorder (PTSD) or depression, which means these findings can’t necessarily be generalised to all children in care. In other words, the evidence suggests that there are multiple factors affecting general intelligence development – in the context of abuse – besides trauma, and these factors include neglect and poverty.
The presence of PTSD appears to affect cognitive functioning. Studies show that children with PTSD subsequent to abuse have lower verbal IQ on assessment, suggesting that the presence of PTSD rather than abuse per se may be more relevant (Saigh, et al., 2006; Hart, & Rubia, 2012). One well-known study examined the relationship between IQ and exposure to domestic violence, using a large sample of twins to control for genetic influences on IQ (Koenen, et al., 2003). In this study, exposure to domestic violence was found to be related to IQ in a dose-dependent way: i.e., the more severe the traumatic exposure, the bigger the impact. The IQ scores of those children exposed to domestic violence was found to be eight points lower than children who were not exposed to violence; after controlling for the effects of genetics and other forms of maltreatment (Koenen, et al., 2003). This suggests that a history of exposure to violence and PTSD may both be important influences on cognitive development.
Problems with memory
There is reasonable evidence that memory is affected by trauma and adversity. Brain structures that are associated with memory consolidation have been found to differ in adults (but not children) who report a history of abuse. For example, adults with a history of abuse have been shown to have smaller hippocampal volume – an area of the brain associated with memory consolidation (Hart & Rubia, 2012; McLaughlin et al., 2014; Teicher et al., 2012). Compared with non-abused children, children with abuse-associated PTSD may also show less effective activation of this area of the brain during a memory recall task (Carrion et al., 2010; McLaughlin, et al., 2014).
Neuropsychological studies of children also support the idea that memory is affected by exposure to trauma and other adversity. Studies of children who have been diagnosed with PTSD in the context of abuse also suggest they may experience memory difficulties, but the findings depend on the way memory is measured.
While a few studies have found no difference in memory performance between children with and without abuse-related PTSD (e.g., Beers & De Bellis, 2002), other studies that use more realistic “everyday” tests of memory do show that children with PTSD secondary to trauma do have poorer memory compared with those without PTSD (Moradi, Doost, Taghavi, Yule, & Dalgeish,1999). In general there is good reason to believe that children who have are experiencing abuse-related PTSD will have difficulty with a wide range of memory tasks (Cicchetti, Rogosch, Gunnar, & Toth, 2010; DeBellis, et al., 2002; McLean, & Beytell, 2016).
Bias in the processing of social/emotional information
There is some evidence that social and emotional information is processed differently among children that have experienced abuse. The amygdala, an area of the brain associated with the automatic (pre-conscious) processing of emotional information, has been shown to be over-responsive to emotional stimuli (e.g., angry faces) in studies of abused children (McCrory et al., 2011; McLaughlin et al., 2014; Pollak, Klorman, Thatcher, & Cicchetti, 2001). Traumatised children are able to identify angry faces more quickly than non-traumatised children, suggesting they are “primed” to detect threat (McLaughlin, et al., 2014; Pollak & Sinha, 2002). Children who have been exposed to traumatic environments also have reduced thickness in an area of the brain responsible for emotional processing of social information (ventro medial Prefrontal Cortex, vmPFC) (De Brito et al., 2013; Kelly et al., 2013; McLaughlin et al., 2014), suggesting this area is less developed in these children compared with non-abused children.
Executive functioning (cognitive flexibility and behaviour regulation)
There is some evidence that executive functioning difficulties can develop as a result of early adversity. Executive functioning is a coordinated set of cognitive skills that includes two broad domains: metacognitive skills (attending to task, planning, organisation, cognitive flexibility) and skills of behaviour regulation (response inhibition, emotional regulation) (Goia, Isquith, Retzlaff, & Espy, 2002).
Neuropsychological research suggests that children who have experienced neglect and physical abuse can experience problems in auditory attention and cognitive flexibility (problem-solving and planning) (Nolin & Ethier, 2007). Children with abuse-related PTSD have been found to have significantly poorer attention and executive function compared with a matched sample of non-maltreated children: they made more errors in tasks of sustained attention, and were more easily distracted and more impulsive than their matched peers (DeBellis et al., 2009; Nolin & Ethier, 2007). One study has found that experiencing PTSD in the context of familial trauma may have more significant impact on executive functioning than non-familial trauma (DePrince Weinzierl, & Combs, 2009).
Compared to non-neglected peers, emotionally neglected children may have less efficient brain activity during tasks that require inhibitory control, suggesting that neglect is associated with poor ability to self-regulate and inhibit responses (Mueller et al., 2010; McLaughlin et al., 2014). This may also be resistant to intervention (McLean & Beytell, 2016).
Summary of the evidence
As a whole, the research suggests that children in care are likely to experience one or more cognitive difficulties. Much more research is needed to explore:
- the impact of timing of abuse;
- whether it matters that the trauma is familial or not; and
- and whether cognitive difficulties are due to abuse per se or the PTSD that arises as a result of traumatic experiences.
In the research reviewed here, PTSD is commonly linked with cognitive functioning, suggesting that it may be especially important to address cognitive vulnerabilities in children showing signs of PTSD.
In general, the evidence base linking abuse and cognitive impairment is not as strong as it is for other factors, including the impairment arising from foetal alcohol syndrome (McLean & McDougall, 2014). Taking into consideration the range of factors that are known to affect cognitive development, the broader literature on cognitive functioning in children in care suggests several areas that can be affected by childhood adversity.
Taken as a whole, the literature suggests that children in care are likely to experience:
- compromised executive functioning;
- difficulty regulating arousal levels in response to emotional and sensory stimulation (high and low emotional responsiveness);
- difficulty with attention and memory;
- distinct patterns of social information processing;
- reactivity to sensory stimuli;
- disruptions to sleep and other circadian rhythms; and
- compromised language development, including difficulty in the comprehension and social use of language despite apparently adequate verbal abilities.
(See Cook et al., 2005; De Lisi & Vaughn, 2011; Lansdown, Burnell, & Allen, 2007; Mc Crory et al., 2010; McLean & McDougall, 2014; Noll et al., 2006; Ogilvie, Stewart, Chan, & Shum, 2011; Perry & Dobson, 2013.)