Friday, November 28, 2008

The Neurobiology of Trauma and the Developing Brain in Childhood

By Louise Maxfield

During exposure to a stressor, the brain initiates a cascade of responses. Glucocorticoids are released to mobilize energy, increase cardiovascular activity, and slow down unnecessary physiological processes. Chronic exposure to extremely high levels of glucocorticoids can seriously damage neurons; this is most evident in the hippocampus which contains a high concentration of glucocorticoid receptors. Various animal studies have shown permanent loss of glucocorticoid receptors in the hippocampus as well as significant damage to the hippocampal neurons, with resulting hippocampal degeneration.

Studies using magnetic resonance imaging (MRI) found reduced hippocampal volume in adults with PTSD. In their combat veteran research, Bremner et al. (1995) compared 26 Vietnam veterans with PTSD to 22 normal veterans, similar in age, sex, race, years of education, socioeconomic status, body size, and years of alcohol abuse. Combat veterans with PTSD had a statistically significant 8% smaller right hippocampal volume and a statistically insignificant 4% smaller left hippocampal volume.

In a similar study with adult survivors of childhood abuse, Bremner et al. (1996) found that those survivors with PTSD had a 12% smaller left hippocampal volume and a statistically insignificant 5% smaller right hippocampal volume. It is not known why persons traumatized as adults had smaller right hippocampal volume and those traumatized as children had smaller left hippocampal volume. The researchers suggest that larger sample sizes, with increased power, might find smaller volumes for both right and left hippocampal volumes. Another possibility is that there is a true difference in patients with early trauma, and that early trauma may interfere with brain development.

Diminished hippocampal size may be either a consequence of trauma exposure or a risk factor for the development of psychiatric complications following trauma exposure. Dysfunction of the hippocampus may be related to the fragmentation of memory that occurs with PTSD and to dissociation.

Similar findings were found by Stein, Koverola, Hanna, Torchia, & McClarty (1997) who measured hippocampal volume using the MRI in 21 women who reported being severely sexually abused in childhood. They compared these subjects to a control group of 21 socio-demographically similar women without abuse histories. A statistically significantly 5% smaller left hippocampal volume was found in the women who reported sexual victimization in childhood, as well as a statistically insignificant smaller right hippocampal volume. Left-sided hippocampal volume correlated highly (r = -0.73) with dissociative symptom severity. Stein et al. suggest that the relationship between symptom severity and hippocampal volume indicates that mesial temporal lobe dysfunction may directly mediate certain aspects of PTSD and dissociative disorder symptomatology.

Possible hippocampal degeneration is only one aspect of the complex picture. Studies on the physiological effects of trauma have found profound and substantial effects within multiple interconnected neurobiologic systems. Exposure to extreme or chronic trauma related stressors can result in abnormal patterns of neurotransmitter and hormonal activity, and in permanent changes in neuronal differentiation and organization. Neurobiological effects are evident in brain stem dysregulation, alterations within the central nervous system, irregularities in cortical function, alterations within catecholamine systems, and dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and the hypothalamic-pituitary-thyroid axis.

Since these effects are pervasive, powerful, and occasionally permanent even for adults, it is apparent that childhood trauma can have a massive impact on the developing brain, with its high levels of plasticity. The child's brain is structured and neuronally organized by experience. There are substantial implications for all aspects of children's development, with potential deficits and impairment in emotional, behavioral, cognitive, and social functioning.

end of article

I have heard before that people suffering from depression, chronic abuse, or stress have a smaller hippocampus. In some cases, antidepressants can reverse at least part of the damage. I did not know that chronic or severe abuse could affect all those other systems, as highlighted in the article above. It mentions the brainstem, which I have been researching, and the HPA axis, which regulates the stress response. If the latter is malfunctioning, it could mean it is not getting the feedback necessary to 'turn off'. I studied this axis in university, so I know how it works. If it is always on, you are under constant stress, constant 'fight or flight'. You will have high levels of cortisol and other chemicals that are meant for short, emergency use. They are damaging if they are in the body for too long. All this could lead to adrenal exhaustion. Of course, I'm purely speculating, but somebody has to if I'm ever going to figure out what is going on with my body, and nobody else seems to be interested in doing it. Anyway, pain and fatigue - my body breaking down - could certainly be associated with a chronic stress response. So could an exaggerated startle response.

Obviously, I have never been to war, nor was I physically or sexually abused as a child. I don't have an official diagnosis of PTSD, but I do experience almost all the symptoms. Doesn't a nervous breakdown or suicidal episode qualify as a traumatic experience? What about living chronically with the fears of 'losing it', being 'discovered', and subconsciously threatened with losing food and shelter? How about twenty odd years of feeling worthless, unwanted, abnormal, and ashamed? Twenty odd years of a voice in your head saying you have to be perfect or else, saying you are so horrible you have to pretend to be someone else, saying you are a burden and in the way, and that it is your fault? Aren't those years full of chronic abuse? I have re-lived intrusively my own "humiliations" over and over again without being able to control or stop it. I jump out of my skin at least once a day. I never feel safe, even behind my locked door in my one-room apartment. Experience shapes your brain, this is a proven fact. What mangled and warped gray matter lays beneath my skull?

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