TRAUMA AND THE NERVOUS SYSTEM

Conversations with Dr. Stephen W. Porges PhD

(An excerpt from the book: Guía de bolsillo de la teoría polivagal)

Dr. Buczynski: I am Dr. Ruth Buczynski, a licensed psychologist for the state of Connecticut and president of the National Institute for the Clinical Application of Behavioral Medicine (NICABM).

Our guest is Dr. Stephen Porges. I believe Stephen’s work will transform the way we understand trauma and other disorders. When someone experiences trauma, what exactly is going on inside?

Dr. Porges: A major problem in understanding neurophysiological responses to trauma is that it has been conceptualized as a stress-related disorder. By placing trauma in this category, important specific features of trauma are lost in the debate about causes, mechanisms, and treatments. The problem lies in the confusion of believing that the human nervous system responds to danger and the risk of death with a common stress reaction that is associated with the sympathetic nervous system and the HPA (hypothalamic-pituitary-adrenal) axis. Therapists and scientists have assumed that the human nervous system has a single defense or stress system, related to the management of “fight/flight” behaviors. The polyvagal theory emphasizes that danger and the risk of death give rise to different defensive response profiles. According to the theory, reactions to danger are associated with accepted notions of the stress response expressed in increases in autonomic activity in the sympathetic nervous system and adrenal glands. However, the polyvagal theory also identifies a second defense system related to the risk of death, which is characterized by the presence of an ancestral pathway of the parasympathetic nervous system that profoundly inhibits autonomic function.

We all know about the negative effects of the “classical” stress response, which interferes with the health-promoting functions of the nervous system. By disrupting the regulation of the autonomic, immune, and endocrine systems, stress generates vulnerability to mental and physical illnesses. This defensive system is described in all academic works of psychology, and is essential in any debate about the links between health and psychological experiences. It is a model described in subdisciplines such as neuroendocrinology, neuroimmunology, psychophysiology and psychosomatic medicine. However, these debates do not describe a second defensive system, whose characteristics do not revolve around mobilization, as is the case with fight/flight reactions, but around immobilization, behavioral blocking and dissociation. Faced with signs of danger, fight/flight behaviors are functionally adaptive, but they are not so much so when escape or physical defense is not possible.

Unlike fight/flight reactions, the response to the risk of death activates a second defensive system, expressed through immobilization and dissociation. When the body immobilizes itself in order to defend itself, it enters a unique physiological state that is potentially lethal. This response is often observed in small mammals, such as the common mouse when it is being hunted by a cat. When a mouse is caught between the cat’s jaws, it appears dead, but it is not. This adaptive reaction of the mouse is called thanatosis, or feigning death. However, it is not a conscious or voluntary response. It is an adaptive biological reaction to the inability to resort to fight/flight mechanisms to defend itself or escape. This response reflects that it is similar to that of a human fainting from fear.

Adding to the difficulties in treating trauma patients is the lack of knowledge of the full range of adaptive biological reactions to threats. Unfortunately, many dedicated doctors who work with these patients are unaware of the defensive system of immobilization. Scientific literature suggests that this weakness is due to the incompatibility of a defensive immobilization system with dominant theories on stress, the axis of which is the contribution of the adrenal glands and the sympathetic nervous system to defensive mobilization strategies.

The polyvagal theory emphasizes that the nervous system has more than one defensive strategy, and that the decision to use the active defensive strategy of fight/flight or freeze and immobilize is not voluntary. conscious mental processes that we attribute to the “executive” functions involved in decision-making.

In some people, certain physical features of an environmental challenge will elicit fight/flight behavior; others may freeze up completely in response to the same physical features.

For some, traumatic events are mere events, but the same events trigger potentially life-threatening responses in others. Their bodies respond as if they were going to die, along the lines of the mouse in the cat’s throat response.