One way that traumatic experiences can negatively effect brain development is through the accumulation of toxic stress. Stress is a normal, necessary part of life and can be a positive factor in helping children develop the skills they need to cope with challenging situations throughout life. Stress stops being a positive thing when it becomes too severe or prolonged and overwhelms the child’s ability to manage.
There are three categories of stress. First is positive stress. This results from adverse experiences which are short in duration. Things that cause positive stress are a visit to the doctor’s office, meeting new people, or attending a new daycare. This type of stress causes minor physiological changes including increased heart rate and changes in hormone levels, specifically a rise in cortisol. With the support of caring, trustworthy adults, children lean how to manage and overcome positive stress. Learning to cope with normal stress is an important part of the developmental process.
The next type of stress is called tolerable stress. Tolerable stress refers to adverse experiences that are more intense but relatively short in duration. Examples of this might include parent’s divorce, a car accident, or death of a loved one. This causes more serious, but temporary responses in the child’s stress response system and the negative effects are buffered by supportive relationships.
The third type of stress and the one that we are most concerned with is toxic stress. Toxic stress results from intense adverse experiences that are chronic and sustained over a long period of time – weeks, months, or years. The most common type of toxic stress is maltreatment in the form of abuse or neglect. As a result of this type of stress, the stress response system becomes activated for a long period of time, which can lead to permanent changes in brain development. For example, toxic stress can impair development of synaptic connections in the brain, literally resulting in a smaller brain in children who are exposed to chronic, toxic stress. The frequent flooding of stress hormones also leads to a low biological threshold for stressful experiences, causing individuals exposed to toxic stress to become overly reactive to adverse experiences throughout their lives. High levels of stress hormones like cortisol actually suppress the body’s immune response which leaves people vulnerable to infections and chronic health problems. High levels of cortisol also damage the hippocampus which is the part of the brain responsible for learning and memory, causing cognitive deficits that continue into adulthood.