Secondary traumatic stress is a risk we incur when we engage empathically with an adult or child who has been traumatized. Charles Figley (1995) defines secondary traumatic stress as "the natural consequent behaviors resulting from knowledge about a traumatizing event experienced by a significant other. It is the stress resulting from wanting to help a traumatized or suffering person." Until recently, when we spoke about persons being traumatized we were speaking of those people who were directly exposed to the trauma. It has only been recently that researchers and practitioners have acknowledged that persons who work with or help traumatized persons are indirectly or secondarily at risk of developing the same symptoms as persons directly affected by the trauma. Clinicians and parents who listen to their clients or children describe the trauma are at risk of absorbing a portion of the trauma.

Secondary traumatic stress may also be used interchangeably with the term "vicarious" trauma. This can be somewhat confusing. In our work, we use the term vicarious trauma to refer to the traumatic impact on those who feel the intensity of the traumatic event through another person. Children of Vietnam veterans, for example, have been reported to exhibit emotional, behavioral and physiological symptoms similar to their parents with post-traumatic stress disorder (PTSD). Parents of children suffering from chronic, painful medical conditions can become vicariously traumatized. Significant vicarious traumatic symptoms were experienced throughout the United States following the horrific events of September 11th. The power and intensity of the actual event can be powerful enough to impact others even though they were not themselves witness to or threatened by the actual experience.