There are three types of stress responses: positive, tolerable, and toxic. These terms refer to the effects of the stress response systems on the body, not to the stressful event or experience itself. 

Positive stress:
A normal, brief reaction that is essential for development, characterized by brief increases in heart rate and mild elevations in hormone levels. Examples include the first day at a new childcare setting or the temporary fear and discomfort that can come with receiving an immunization, with supportive relationships to help buffer against a child’s stress response.  

Tolerable stress:
More severe, longer-lasting reactions that activate the body’s alert systems to a greater degree, such as the loss of a loved one, a natural disaster, or a frightening injury. If the stress activation is time-limited and buffered by relationships with adults who help the child adapt, the brain and other organs recover from what might otherwise be damaging effects. 

Toxic stress:
Occurs when a child experiences strong, frequent, prolonged adversity—such as physical or emotional abuse, chronic neglect, caregiver substance abuse, exposure to violence, climate-driven extreme weather events like flooding, and/or the accumulated burdens of family economic hardship—without supportive relationships to buffer against stress. This can disrupt brain and organ development, potentially leading to lifelong health issues, underscoring the importance of policies and programs that support caregivers who can help protect children from toxic stress during times of adversity.