The effect of child abuse on the brain and the impact of stress hormones on emotional and cognitive development
Maltreatment, no matter whether it is abuse, neglect, abandonment or witnessing violent acts, can lead to enduring negative changes in the still developing brain of a child. Each time there is some sort of trauma, the brain suffers a particular change. So far, research have noted changes in the prefrontal cortex, the cerebellum and the limbic system (Wheeler T, 2006) It is important to point out that infancy and early childhood are times for rapid brain development and formation of dendritic connections. Of course, they continue to develop throughout adolescence an early adulthood, but are even more vulnerable earlier in life (Kalat J, 2003).
The prefrontal cortex is the most anterior part of the frontal lobe of the brain that is involved in critical thinking and judgment as well as any behavior that, in one way or another, depends on the context. Therefore, people with damaged prefrontal cortex often cannot modify their behavior and become inflexible in changing situations, which can make their reactions and behavior too impulsive and socially unacceptable (Kalat J, 2003). Damage to the prefrontal cortex can eventually result in many deficits such as not being able to regulate motivation and efforts as well as impaired short-term and long-term goal-directed behavior. In addition, damage and disruption of prefrontal cortex functions due to any type of abuse may lead to not being able to integrate positive emotions. Thus, the person is stuck in a negative stance of fear and anger, and cannot engage in experiencing positive emotions. Needless to say, this may lead to developing depression, antisocial or borderline personality disorders (Wheeler T, 2006).
The cerebellum is a large structure in the hindbrain that is mainly known for controlling movement, achieving balance and coordination (Kalat J, 2003). However, it also plays a role in attention and emotions, as well as in regulating the limbic system (Wheeler T, 2006). It is important to note that many people with psychiatric disturbances have certain abnormalities in the cerebellum (Wheeler T, 2006). This is probably so, because in cases of childhood abuse the cerebellum is extremely vulnerable to the stress hormones that are present in large amounts during stress, trauma or abuse. The changes that occur then can result in depression or hyperactivity, and inattention. Also, the cerebellum is considered to play a role in suppressing irritability. Therefore, abnormalities or damage to the cerebellum may cause chronic irritability and make the person seek external means, such as drugs, to deal with that (Wheeler T, 2006).
The limbic system is the forebrain area next to the brainstem that includes a number of interdependent structures under the cerebral cortex that deal with motivation and is critical for regulating emotions, sexual activity, eating, drinking, anxiety, and aggression (Kalat J, 2003). The hippocampus and the amygdala are essential parts of the limbic system, and are crucially important for controlling the emotional response to a particular situation. They also take part in memory formation and learning (Wheeler T, 2006). Prolonged and continuous exposure to stress hormones can cause serious damage to these parts of the limbic system and, thus, disrupt mood regulation, memory, and one’s way of interpreting the environment. Besides, damage to the limbic system can lead to epileptic seizures and abnormal EEGs that usually affect the temporal lobe of the left hemisphere. Usually, damage to the left hemisphere is associated with poor verbal development, but, more importantly, with aggression, self-destructive behavior and suicide (Wheeler T, 2006).
What is stress? Many things can be considered stressful for an individual, including insufficient nutrition, lack of rest, overstimulation, especially of the fear-related response system, not to mention abuse, neglect or witnessing violence or death (Gunnar & Vazquez, 2001). The prolonged exposure to stress and, therefore, the produced stress hormones in the body, can be very serious and especially harmful to the infants and young children (Gunnar & Vazquez, 2001). In fact, exposure to stress activates two body systems: the autonomic nervous system that prepares the body to react quickly to whatever stimuli in the environment; and the HPA-axis – the hypothalamus, pituitary and adrenal cortex.
The HPA-axis reacts more slowly, but is critically important in prolonged exposure to stressors (Kalat J, 2003). The activation of the hypothalamus stimulates the ‘master gland’ (the pituitary gland) to secrete adrenocorticotropic hormone (ACTH) that, in turn, stimulates the secretion of cortisol. Cortisol is generally regarded as ‘The’ stress hormone. It helps the body mobilize energy and respond to stress quickly, but has negative effects in the long run, since it enhances metabolism and elevates blood sugar levels (Kalat J, 2003). Other stress-related hormones are corticosteroids, corticotrophin release hormone (CRH), epinephrine, norepinephrine and others (Gunnar & Vazquez, 2001). Serotonin is also very important for the adequate coping with stress. Therefore, abnormal function of serotonin is associated with some depression and anxiety-related disorder, such as BPD.
Research has proven that elevated stress hormone levels can cause malfunctions in the amygdala and hippocampus (Gunnar & Vazquez, 2001). Severe or merely constant exposure to stress may lead to the shriveling of certain dendrites in the hippocampus, which can cause its degeneration and malfunction (memory loss and inability to control the release of other stress hormones) (Gunnar & Vazquez, 2001). As a matter of fact, shrunken hippocampus was found in autopsies of children who have experienced repeated abuse or in people who were suffering posttraumatic stress disorder. In addition, disruption of the HPA-axis that is also related to exposure to stress in early age is associated with depression, inattention, and poor memory (Gunnar & Vazquez, 2001). The hippocampus is a particularly vulnerable brain structure, especially during infancy and childhood, when it is still developing (Gunnar & Vazquez, 2001).
If too many stress hormones are being produced in the early stages of development, the developing brain may be permanently damaged, becoming incapable of initiating a normal stress response. It may either overproduce stress hormones, so that the person becomes hyper-vigilant, fearful and always on the alert, or it may underproduce stress hormones so that the person becomes “emotionally flat”, sad and angry (Berger, 2005). A study of Cicchetti & Rogosch (2001) identified a lot of “atypical cortisol regulation patterns” that are obvious among children that have been maltreated (Gunnar & Vazquez, 2001). Studies like this are evidence for the correlation between child maltreatment and the disrupted function of certain brain structures that cause inflexibility in behavior, such as depression, chronic stress, anxiety, aggression and many others that can often be associated with a number of illnesses and disorders, Borderline Personality Disorder among them.
Many of the brain abnormalities that have been studied in abused and neglected children are located in the left hemisphere. Very often, in children, victims of abuse, there were fewer dendritic connections between different areas in the left hemisphere (Gunnar & Vazquez, 2001). Children that had showed such abnormal results demonstrated self-destructive or aggressive behavior, as well as certain disturbances in behavior, thinking and physiology (higher blood pressure, heart rates temperature, hypervigilance) (Gunnar & Vazquez, 2001). Since these could all be characteristics of a borderline personality patient, the results give food for thought as to the relation between abuse in childhood and the development of the disorder.
Studies of neglected children found that their cortex was about 20 percent smaller than that of a control group of subjects (children) who have not suffered neglect (Gunnar & Vazquez, 2001).