Biology 202
2002 Second Paper
On Serendip

What doesn't kill you makes you stronger. How true is this axiom? In many cases, dealing with life's problems will indeed help create a stronger person. There are times, however, when this may not be true.

Child abuse is a widespread problem in America and beyond. In Pennsylvania alone, there were 5109 physical injuries in kids ages 5-14 in 1989, and a further 55 fatalities in children age 4 and under, all due to child abuse (1). For many years, experts believed that the negative effects of child abuse, such as emotional problems, flashbacks to traumatic events, and even learning problems, were psychological phenomena only, able to be cured with therapy. Now, however, beliefs are being changed with the help of tools such as MRI imaging, able to detect actual changes in brain anatomy, and it appears that what doesn't kill you may still permanently weaken you, at least when it comes to child abuse.

The chief danger to the brain in child abuse, besides direct injury by the abuser, is the stress placed on fragile, developing tissue. Traumatic stress placed on the brain, such as that caused by abuse, will activate the locus ceruleus, which through a release of the neurotransmitter norepinephrine will cause the release of neurotransmitters such as epinephrine, dopamine, and more norepinephrine (2). These neurotransmitters are called catecholamines and are complemented by glucocorticoid stress hormones such as cortisol (2). Stress hormones and neurotransmitters are necessary to the normal function of the brain, and are to some point beneficial, but unusually high levels of these chemicals caused by abuse, especially over an extended period of time, can be very harmful (3). When levels of glucocorticoid hormones are elevated for an extent of several days due to stress, the neurons receiving these hormones begin to be damaged (4). Neurons begin to atrophy and the growth of new neurons is halted (4). If the stress continues for too long, neurons will die (4). This problem is exacerbated by the hormones themselves, which due to their water-insoluble properties will stay in the bloodstream for hours or days (3). The water-soluble neurotransmitters, on the other hand, only last for seconds (3). This persistance of the stress hormones makes it hard for the brain to return to its natural, unstressed state.

The brain develops in such a way that it leaves itself vulnerable to these negative influences. The prenatal brain develops an overabundance of neurons, some of which are then carefully eliminated before age 4 (5). In a process similar to this, the amount of synapses between neurons is built up during early childhood and then pruned back for the next 30 years of life (5). These two processes are both disturbed by elevated levels of stress hormones (5). The two centers of the brain with the most postnatal changes, including the growth of new neurons after birth, are the hippocampus, which is part of the limbic system, and the cerebellar vermis (6). The hippocampus is in charge of creating and retrieving memories, working together with the other parts of the limbic system, such as the amygdala, which records the emotions for each memory. The vermis controls the production and release of two of the catecholamine neurotransmitters, dopamine and norepinephrine (6). Both the vermis and the limbic system have higher concentrations of receptors for the stress hormone cortisol than anywhere else in the brain (6). Due to this fact, these still-developing areas are the most vulnerable to the damage done by elevated levels of stress hormones.

The limbic system shows the most dramatic effects of abuse. As stated before, an overexposure to stress hormones will cause the atrophy and eventual destruction of neurons, while halting the growth process of new neurons. This effect is clearly seen in MRI brain scans of adults who were abused as children: the left side of the hippocampus is markedly smaller than the right (1). Interestingly, when similar MRI testing was performed on a group of young people, ages 18-22, who had also suffered abuse in childhood, the left hippocampus was found to be equal to the size of the right (1). There are several hypotheses to explain this phenomenon. One is that the steady growth of the hippocampus through three decades prevents a change from being seen until later on in life (5). Another possible explanation is that abuse of alcohol or use of cocaine, used as an escape from painful memories of abuse, could cause the decrease in the hippocampus seen in older subjects (5).

Another alarming indicator of damage to the limbic system can be seen in brain-wave abnormalities detected by an electroencephalogram (EEG) (6). Temporal lobe epilepsy is a condition in which the limbic system is subjected to an "electrical storm" of wayward brainwaves, causing various symptoms of nausea, tingling, or vertigo (6). Tests performed by Martin Teicher in 1994 on 115 children and adolescents, abused and non-abused, showed that 54% of those who had undergone abuse early in life showed abnormalities on the EEG, while only 27% of those who were not abused showed abnormalities (6).

The effects of the overload of stress hormones on the vermis are is difficult to tell. However, it is clear that the vermis plays an essential role in the brain (6). Problems in the vermis are linked to bipolar disorder, autism, schizophrenia, and attention-deficit/hyperactivity disorder (ADHD) (6). The vermis is also partially in charge of the electrical activity in the limbic system, and an electrical stimulus applied to the vermis causes seizure activity in the limbic system to halt (6). If this suppression of improper electrical signals in the limbic system is part of the vermis' regular duties, damage to the vermis may be partially responsible for the brain-wave abnormalities of the limbic system described in the paragraph above.

Child abuse has a distressing effect upon learning ability as well. The hippocampus performs the essential task of storing and retrieving verbal memories, for which it retains a plasticity in order to learn and remember (6). However, the hippocampus is not the only part of the brain affected by abuse. In a study of children and adolescents diagnosed with posttraumatic stress disorder (PTSD) due to physical or sexual abuse, an unsettling relationship was seen between brain development and degree of abuse (5). The intracranial volume of PTSD subjects was smaller than the control group, and the longer the subject had been abused, the smaller the intracranial volume was (5). This decrease of intracranial volume was also shown to have a direct correlation to the decrease of IQ in the PTSD subjects, and the longer the child had been abused, the lower the IQ would be (5). Brain size in general also decreased as intensity and length of abuse increased (5).

The possibility of mental disorders is also raised. In the same study, the PTSD subjects were found to have larger lateral ventricles the greater the extent of abuse was, which is probably caused by the destruction of neurons due to the overabundance of stress hormones (5). While no direct link has been made, enlargement of lateral ventricles is a symptom of many mental health problems, such as schizophrenia, Alzheimer's disease, alcoholism, bipolar disorder, and depression (5).

The proof of brain damage due to child abuse is plain. Rather than simply causing emotional or psychological distress, child abuse causes the brain to physically "rewire" itself. There is a theory that this rewiring is a throwback to the earlier history of humans, in which increased aggression and fear served to increase the lifespan of the beleaguered human (6). Some even believe that the promiscuity sometimes seen in teens and adults who were abused as children is a continuation of that pressure to survive: if survival is dubious, reproduction is best done as soon as possible (6).

The conclusion of "rewiring" the abused brain presents a far more depressing view of the many behavior problems apparent in abused children, for then a great deal of the aggression, depression, and learning problems of an abused child are physical rather than emotional, and thus will require more than a visit to a therapist to fix, if indeed they can be fixed at all. This conclusion raises more questions. How to fix the "scarring" of the brain caused by trauma in childhood? How much of the emotional and learning problems of an abused child can be fixed, and how many are physical phenomena? Most important of all, perhaps: How to prevent the cycle of abuse from continuing on into another generation?

References

1) Kolko, David J. "Characteristics of Child Victims of Physical Violence: Research Findings and Clinical Implications." Journal of Interpersonal Violence 7.2 (1992): 244-276

2)< href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T4S-3WK3RV4-3&_user=400777&_coverDate=05%2F15%2F1999&_alid=40836662&_rdoc=1&_fmt=full&_orig=search&_cdi=4982&_sort=d&_st=13&_acct=C000018819&_version=1&_urlVersion=0&_userid=400777&md5=b56f7b8e13ccaf122404bcc148bf3926">Developmental traumatology part I: biological stress systems, an article about the effects of stress hormones upon the developing brains of children with post-traumatic stress disorder

3)Development of the Cerebral Cortex: XII. Stress and Brain Development: 1, an article from the Journal of the American Academy of Child and Adolescent Psychiatry, dealing with the effects of stress hormones and neurotransmitters upon the brain in situations of extreme stress

4)Development of the Cerebral Cortex: XIII. Stress and Brain Development: II, an article from the Journal of the American Academy of Child and Adolescent Psychiatry, about the damaging effects of stress hormones on the developing brain

5)Developmental traumatology part II: brain development, an article detailing a study of the effect of post-traumatic stress disorder upon the brains of abused children

6) Teicher, Martin H. "Scars That Won't Heal: The Neurobiology of Child Abuse." Scientific American 286.3 (2002): 68-75


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