HealthJune 11, 2015

Understanding 'defense cascade' may help in treating victims of trauma

The well-known "fight or flight" response is part of the inborn series of defense/fear responses activated in reaction to threats. Understanding the steps of the defense cascade can help in forming effective treatments for patients dealing with persistent aftereffects of trauma, according to a review in the Harvard Review of Psychiatry. The journal is published by Wolters Kluwer.

Child and adolescent psychiatrist Kasia Kozlowska of The Children's Hospital at Westmead, Australia, and colleagues explain the five steps of the defense cascade, in a framework that integrates current neurophysiological findings with clinical experience. They also discuss effective interventions to shift the "signature neural pattern" of each step of the cascade, with the goal of unlocking patients' responses to past traumatic experiences.

The defense cascade and responses to trauma

Kozlowska and colleagues review the characteristics and neurobehavioral basis of the defense cascade—"a continuum of innate, hard-wired, automatically activated defensive behaviors" in response to threats. In humans as in animals, the cascade occurs in a series of five steps:

  • Arousal:  muscles tense, breathing and heart rate increase as the body prepares for action
  • Fight or flight:  active defense response for dealing with threat
  • Freezing:  a fight-or-flight response put on hold
  • Tonic immobility:  inability to move or call out; shut down in the face of fear. A variation is collapsed immobility, with loss of muscle tone and changes in consciousness. Tonic and collapsed immobility are "responses to inescapable threat or strategies of last resort."
  • Quiescent immobility:  after the threat or danger has passed, a state of quiescence that promotes rest and healing

Animals are generally able to return to their normal mode of functioning once the danger is past. However, as Kozlowska and coauthors explain, "Humans often are not, and they may find themselves locked into the same, recurring pattern of response tied in with the original danger or trauma."

The authors detail what's going on in the brain and nervous system through each step in the defense cascade. They believe that understanding the signature pattern of each response can help in addressing the continued defensive states seen in patients with a history of traumatic experiences or events.

The article presents clinical vignettes of traumatized patients with reactions corresponding to each step of the defense cascade. For example, a combat veteran may react with suspicion and rage (fight or flight) to perceived threats; traumatized children may experience episodes of withdrawal or fainting (tonic or collapsed immobility) when reminded of their experiences.

Recognizing and understanding these reactions enables clinicians to design interventions "to manage the mind-body states that are the human expression of the defense cascade."  Clinicians can use—and patients can learn—targeted interventions to decrease arousal, target processing of traumatic memories, and manage mind-body states reflecting each step of the cascade. Understanding the biological basis of the defense responses can also help alleviate guilt or other negative emotional reactions experienced by some trauma victims.

Kozlowska and coauthors believe that their framework can help mental health professionals and lawyers—including those working with clients in the military or law enforcement or assisting victims of sexual abuse—to understand the responses that make up the defense cascade. They conclude, "We hope that this model, coupled with the clinical vignettes, will help clinicians to recognize and differentiate these defensive states in their daily work, and that our analysis will provide them with ideas and options for treatment, so as to unlock the patient's pattern of trauma response and break the cycle of suffering."

The article has been made available on an open access basis; it is available free for download from the Harvard Review of Psychiatry website.

Click here to read "Fear and the Defense Cascade: Clinical Implications and Management."

Article: "Fear and the Defense Cascade: Clinical Implications and Management" (doi: 10.1097/HRP.0000000000000065)

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