Definition of Terms
Stressors are the events that stimulate stress reactions. Stress reactions are the body's chemical and neural responses that promote survival. Whether stressful events are toxic, tolerable, or positive depends on how much of a bodily stress response they provoke and how long that response lasts. These, in turn, depend on whether the stressful event is controllable, whether the child has safe relationships to turn to for support, and how often and for how long the body's stress system has been activated in the past.
Toxic Stress produces frequent, prolonged, and high level reactions of the body's stress management system. Stressful events that are chronic, uncontrollable, and/or experienced without the child having access to support from caring adults tend to provoke these types of toxic stress responses, and such responses can have an adverse effect on brain architecture. In the extreme, such as in cases of severe, chronic abuse, toxic stress may result in the development of a smaller brain. Less extreme exposure to toxic stress can change the stress system so that it responds at lower thresholds to events that might not be stressful to others, thereby increasing the risk of stress-related physical and mental illness.
Tolerable Stress produces large bodily stress responses that could potentially affect brain architecture, but these responses occur for briefer periods which allow the brain to recover and thereby reverse the effects of stress chemicals and problematic brain signals. In addition to their brevity, one of the critical ingredients that make stressful events tolerable rather than toxic is the presence of supportive adults who create safe environments that help children learn to cope with and recover from significant stressful experiences, such as the death or serious illness of a loved one, a frightening accident, or parental separation or divorce. In many circumstances, tolerable stress can have a positive outcome. Nevertheless, it also can become toxic stress in the absence of supportive relationships or if the stressful event itself damages or disrupts the relationships that provide the child a sense of safety and security.
Positive Stress produces small, short-lived bodily stress responses, such as brief increases in heart rate or mild changes in the body's stress hormone levels. Stressful events that provoke positive stress responses tend to be those that a child can learn to control and manage with the support of caring adults, and which occur against the backdrop of generally safe, warm, and positive relationships. The challenge of entering a new child care setting, dealing with frustration, confronting things that provoke mild fear (e.g., overcoming the fear of animals or meeting new adults) all can be positive stressors if a child has the support needed to experience a sense of mastery.