Stress in medicine: Strategies for caregivers, patients, clinicians—Biofeedback for extreme stress: Wounded warriors

Author and Disclosure Information



Posttraumatic stress disorder (PTSD) is a severe anxiety disorder whose symptoms emerge following exposure to extreme stress, such as those encountered in the battlefield or as a result of sexual abuse or natural disasters. The ability to employ coping mechanisms affects the disorder’s presentation as well as the frequency, intensity, and duration of the symptoms. The “Wounded Warrior” program at East Carolina University (Greenville, NC) was developed to promote the functional independence of US Marines, including those with PTSD.


Walter Cannon coined the “flight or fight” response to stress in the early 20th century, in which he emphasized the importance of the parasympathetic system.1 In 1988, Folkow clarified the description as an immune response to stress.2 The stress response is now understood to be a neuroendocrine function that includes a feedback loop between the hypothalamus and the pituitary and adrenal glands; stimulation of the hypothalamus promotes secretion of corticotropin-releasing hormone (CRH) into the hypophyseal portal system, which supplies the anterior pituitarywith blood. CRH stimulates the secretion of adrenocorticotropic hormone into the bloodstream by the pituitary, prompting the adrenal glands to release the stress hormone cortisol.

Cortisol mobilizes the body’s defenses to meet the challenge of an adverse situation. It modulates the stress response by inhibiting the further release of CRH by the hypothalamus. Cortisol thus protects healthy cells and tissues by inhibiting an overreaction from the immune system. Without this protective effect, the interaction between the brain and the immune system can become dysregulated, increasing the risk of immune disorders.


The central nervous system that regulates the overall balance of the autonomic nervous system (ANS) has been called the central autonomic network (CAN).3 The CAN helps control executive, social, affective, attentional, and motivational functions. Therefore, the old paradigm of simply decreasing hyperarousal of the ANS to treat negative affective states and dispositions is inadequate. Instead, restoring the appropriate relationship between the ANS and the central nervous system is the aim behind interventions to treat PTSD.

Autonomic, cognitive, and affective functions assist humans in maintaining balance when confronted with external challenges. The CAN controls inhibitory or negative processes that permit specific behavior and redeploy resources needed elsewhere. When negative circuits are compromised, positive circuits develop, resulting in hypervigilance, the symptoms of which can be devastating and, if not ameliorated, can develop into permanent conditions. In one study,Vietnam veterans with PTSD had an 8% reduction in the volume of their right hippocampus compared with veterans without PTSD. Another study calculated a 26% reduction in the left hippocampus and a 22% reduction in the right in veterans with the most severe PTSD compared with veterans who were in combat but had no PTSD symptoms.4

A common subcortical neural system regulates defensive behavior, including autonomic, emotional, and cognitive behavior. When the prefrontal cortex is taken “off line” for whatever reason, parasympathetic inhibitory action is withdrawn, and relative sympathetic dominance, associated with defense, occurs.


The question then arises of how to train the ANS to avoid hypervigilance. Growing evidence supports the use of heart rate variability as a predictor of hypervigilance and inefficient allocation of attentional and cognitive resources.

The overall objective of heart rate variability training is to decrease ANS hyperarousal and to improve its balance. “Wounded warriors” learn to control ANS responses to stress-producing stimuli (eg, thoughts, memories, and images associated with combat). The goal of training is to decrease arousal and maintain ANS balance for increasing lengths of time.

Once it was observed that alpha waves were dysfunctional in vulnerable populations, protocols were developed to train alpha and theta waves as a method of improving function. Peniston and colleagues5–9 showed that increased alpha and theta brain wave production resulted in normalized personality measures and prolonged the period of time before relapse in alcoholics. This protocol has also shown efficacy as an intervention in depression and PTSD.


The US Department of Defense is studying a combination of central nervous system biofeedback with ANS biofeedback, with the goal of restoring and maintaining tone between the systems.

The training program used in the study lasts 1 month, and starts with a session for preassessment, 16 biofeedback sessions (four per week), a postprogram evaluation, and a 3-month followup. Each week, participants are exposed to stress-producing stimuli that increase in intensity:

  • Week 1: Stroop Color Word Test, math stressor, talk stressor/everyday events
  • Week 2: Talk stressor, combat experiences
  • Week 3: Images and sounds of combat
  • Week 4: Virtual Baghdad or Afghanistan (virtual reality exposure)

Each biofeedback session consists of 5 minutes of baseline evaluation; 5 minutes in which the veteran is subjected to the weekly stressor; 20 minutes of heart rate variability and neurofeedback training; 5 more minutes of training with the weekly stressor; 20 more minutes of heart rate variability and neurofeedback training; and finally 5 minutes of recovery.

Figure. Before (top) and after (bottom) heart rate variability training training. The patient’s heart rate after completing training has markedly less variation.
Preliminary clinical data indicate decreases in ANS hyperarousal and increases in parasympathetic activity (Figure). Reports on the Patient Health Questionnaire Short Form (PHQ SF-36) indicate positive changes in physical symptoms and decreases in symptoms of depression, panic, and anxiety. Outcome measurements will include changes from heart rate variability training; the Posttraumatic Stress Checklist; PHQ SF-36; Profile of Mood States; salivary alpha-amylase changes; a behavioral questionnaire assessing nutrition habits and alcohol, drug, and nicotine use; and the Self-Satisfaction Inventory.


Dysfunction in the balance of both the ANS and central nervous system is associated with symptoms of PTSD in combat veterans. Methods that are designed to restore balance in these systems are needed to ameliorate these symptoms. Biofeedback and neurofeedback are safe methods with which to achieve these goals.

Next Article: