A major way by which childhood abuse can disrupt normal brain activity is by diminishing its capacity to handle stress. Stress is more than the worry and distress we experience when the circumstances of life push us beyond our limits. The body’s response to stress is a complex biological mechanism. When the brain senses that the body is being taxed beyond its usual capacity, it initiates the stress response by releasing a substance called corticotrophin releasing hormone, or CRH. CRH stimulates the pituitary gland to release ACTH that, in turn, triggers the release of the stress hormone, cortisol, from the adrenal glands. Cortisol marshals the body’s resources to provide the extra energy and endurance to meet the demands being placed upon it. Once, this might have been escaping an angry mastodon. Today, it would more likely be getting used to a new job, a nasty divorce, or recovering from surgery.
The stress-induced switch into physiological overdrive is designed to be brief. In fact, among the many things that cortisol does in the body, one of the most important is to feed back to the brain and start to shut the stress response down. Cortisol does this by binding to specific receptors in the brain. Cortisol fits the receptor, like a key in a lock, and turns the response off. One of the problems in those that have suffered severe, childhood abuse is that the brain’s turn-off switch for the stress response is disabled
A study published in 2009 in the prestigious journal Nature Neuroscience revealed part of the reason why adults who were abused as children have abnormal stress responses. The grim details of the study included comparisons of the brains of individuals who had committed suicide vs. those who had died natural deaths. Among those who had committed suicide were some who had suffered severe childhood abuse and others who had not. It was found that among those who had suffered abuse, there were fewer of the special cortisol receptors in the brain that allow cortisol to turn off the stress response. It was further found that the section of DNA responsible for maintaining adequate numbers of these receptors had been methylated. They were no longer in full operation.
When the stress response won’t shut off and cortisol levels remain high in the brain, bad things can happen. Whereas bursts of cortisol help bolster the brain’s supply of glucose and chemical messengers, sustained high levels of cortisol can cause damage. Cortisol diminishes the brain’s response to the chemical messenger, serotonin, while it enhances the response to norepinephrine. Persisting high levels of cortisol also decrease levels of Brain-derived Neurotrophic factor, a substance that is necessary to maintain and replenish neurons in the brain. These and other changes alter mood, disturb sleep, heighten anxiety, and cause irritability. Consequently, the individual becomes more prone to Major Depression, PTSD, Generalized Anxiety, and other psychiatric disorders.