Childhood Stress and Brain Damage: Too Much Stress Impairs Memory Function

by Carly Hart for PSY377

A student speedily typing a paper that is due in only a few hours has sweaty palms. An adult nervously walking into a job interview feels pounding in their heart and dread in their mind. A young child is breathing heavily as they scramble to clean up evidence of a lamp they broke before their parents can find out. All of these situations are examples of a stress response. Almost everyone can remember a time when they felt both emotional tension and a bodily response to stress, such as an elevated heart rate. The stress response we feel to everyday hassles may make us feel uncomfortable, but it is not a risk to our health. Unfortunately, not everyone is only pestered by lost keys and approaching assignments. A child may be growing up surrounded by abusive family members or crime and poverty. Or they could be exposed to a horrific natural disaster. A child living through these traumas may not be reaping the positive benefits of stress, but instead may experience serious damage to their developing brain. The Adverse Childhood Experiences, or ACE, study found a connection between early childhood stress and adulthood health and behavioral issues (The Adverse Childhood Experiences Study ). This study investigated how certain stressors, such as abuse, related to a plethora of health issues and behaviors, from cancer to depression to the habit of smoking. Early childhood stress has been linked to adulthood psychiatric disorders (Stress load during childhood affects psychopathology in psychiatric patients) and memory impairment (Instrumental learning and cognitive flexibility processes are impaired in children exposed to early life stress). But what exactly does stress do to the developing brain? A deeper look into our nerve cells and genes may give us a glimpse as to the extent to which stress disrupts brain development in childhood.

The hippocampus is closely linked with creating many types of memory, such as memories of events and our physical surroundings. Stress hormones, the chemical substances the body releases while under stress, circulate in the bloodstream and cause changes throughout the body. But, stress hormones also interact with parts of the brain. Stress hormones bind to parts of a nerve cell called receptors and subsequently cause a change. In normal quantities, stress hormone binding causes nonharmful changes to the hippocampus. But, when stress is excessive and long-term, the binding causes damage to the cells of this part of the brain. Prolonged exposure to stress hormones can make cells in the hippocampus unable to receive as many signals from other cells, which means that some cells can’t communicate and respond correctly. Many cells in this area of the brain have strong communication routes with each other, which allows for fast transmissions of information, but high stress reconfigures these routes, which makes it more difficult for cells to communicate. High stress also can kill nerve cells, which will make the hippocampus less equipped to do its job: creating memories. Visible impairment in memory has been observed due to high stress. People who have been exposed to excessive levels of stress do worse on many memory tests (Stress hormones and brain aging: Adding injury to insult).

Overall, the stress caused by daily life tasks is far less harmful than childhood trauma and adversity. A young developing brain is making vital connections and creating important brain structures. Damage and death to nerve cells in the hippocampus, caused by high levels of stress hormones, can cause life-long memory impairment. Evidence suggests that many other areas of the brain are affected by stress in harmful ways as well. For example, one section of our brain that is involved in regulating emotions, especially fear, has been found to become overactive due to exposure to prolonged stress, which can cause excessive anxiety and even symptoms of Post-Traumatic Stress Disorder (PTSD) (Amygdala transcriptome and cellular mechanisms underlying stress-enhanced fear learning in a rat model of posttraumatic stress disorder). Thinking back to the ACE study, it is important to note that an unsettling number of the participants (more than half of the sample!) had faced at least one major traumatic experience during their childhood. This indicates that many people are affected by an event that can cause unhealthy stress levels. There are so many people experiencing intense levels of stress at some point during their childhood, so it is important to ask how many of those children will experience some sort of brain damage. An even more vital question is, how can we lessen, reverse, or avoid these effects?