December 1, 2011  

Losing sleep

A Ranger argues that prolonged stress and sleep deprivation undermine training — and even troops themselves

At the U.S. Army Ranger School, one of the military’s most renowned courses for combat arms and special operations forces, soldiers are trained and tested on individual and small-unit war-fighting skills in a high-stress environment. To pump up the pressure, the soldiers are deprived of much sleep during the 61 days of training. Many wash out. Of 89 infantry lieutenants who began Ranger School with me in the fall of 2001, only eight made it straight through to graduation.

But the Rangers who graduate have proved that they can overcome adversity and lead under pressure. Soldiers learn that their bodies can endure far more adversity than they previously thought possible, and that they can still fight effectively under high stress and after long deprivation of food and sleep. Ranger School makes other challenges pale in comparison; the training sets a high bar that is unlikely to be surpassed thereafter.

So why argue with apparent success? Recent neuroscientific findings show that the prolonged stress and sleep deprivation of Ranger training actually work against learning and, moreover, can degrade long-term mental and physical health. The same is true of other elite training programs — and of many troops who serve on lengthy combat deployments.

Applying the new research can help the Army better train soldiers to handle combat stress, and that could lead to more efficient combat operations, less collateral damage and casualties, and fewer soldiers who experience post-traumatic stress disorder (PTSD).

Neuroscience of stress

Stress is a natural and adaptive reaction that allows individuals to cope and respond to threats. Short bursts of stress during military training can be beneficial; they expose soldiers to specific combat situations they will face, teach them how to manage the stressor and foster the warrior ethos.

But evolution has geared the human stress response to last about 30 seconds, enough to facilitate fight or flight. Evolution has not adapted our brains or bodies to handle weeks or months of prolonged stress — the kind that can feature in the two-month Ranger School and yearlong combat tours.

In a stressful situation, the brain’s amygdala activates the body’s hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, which produce the physiological and metabolic changes of the physiological stress response. The amygdala is itself regulated by two other parts of the brain. The hippocampus helps place the stress in context, while the prefrontal cortex, connected to executive function and working memory, helps abate fear.

The prefrontal cortex helps a soldier to feel in control of a battlefield stressor and make sound decisions under fire. A 1999 study found that the prefrontal cortex develops into the mid-20s. Most soldiers are in their early twenties, with prefrontal cortex still in development. Moreover, prolonged stress and sleep deprivation may hinder the healthy development of the prefrontal cortex. In particular, the size of the medial prefrontal cortex is correlated to the ability to control fear. In people with PTSD, a weak medial prefrontal cortex response fails to modulate a hyperactive amygdala, and the initial fear response does not abate.

Prolonged stress cripples the hippocampus, which is full of cortisol receptors and therefore highly responsive to stress signals. It particularly degrades executive function, motor skills and declarative memory processes. The excess cortisol of sustained stress degrades hippocampal plasticity (capacity for continuous alteration of neural pathways) and hippocampal dendritic morphology (disconnects neural networks by decreasing the number of apical dendrite branch points).

Neuroscientists found that the excess cortisol can stop hippocampal adult neurogenesis (creation of new neurons) and can even kill hippocampus cells, essentially causing regional brain damage. The hippocampal atrophy can hurt soldiers’ learning, decision-making and long-term health. This hippocampal atrophy also increases risk for PTSD. Researchers Rachel Yehuda and Joseph Ledoux found that the smaller hippocampus makes it more difficult for those veterans to contextualize and reinterpret the traumatic memories in a way that facilitates recovery.

Prolonged stress is associated with problems in most physiological systems as well. The greater amygdala neuronal activity in stressed people is associated with fear and anxiety disorders, depression and hallucinations. Although most Ranger students believe that their hallucinations are due solely to sleep deprivation, it is possible that the protracted stress of Ranger training is a contributing factor.

The hyperactive amygdala in stressed people is also associated with suicide. This could be related to the high suicide rate among soldiers who have experienced the prolonged stress of a combat tour. The 2007 suicide rate among veterans aged 20-24 was 22.9 per 100,000, four times higher than nonveterans the same age. That represents a 26 percent increase in just two years. This offers the military yet another reason to ease lengthy deployments and prolonged stress exposure for soldiers.

Finally, prolonged stress hurts the cardiovascular and immune systems. Under extended stress, the frequent over-production of cortisol can result in Cushing’s disease, Addison’s disease or cardiovascular diseases. The excessive adrenaline creates scars in the blood vessels that elevate the risk of heart attack and stroke. Protracted stress decreases the white-blood cell count and affects the part of the immune system that produces antibodies. People with chronic stress are more likely to suffer autoimmune disorders (for example, cellulitis, common in Ranger School) and suffer from the common cold three times more often.

In summary, while the stress response is important for survival, enduring prolonged stress is unhealthy for human brains and bodies.

Sleep deprivation

One of the most difficult aspects of Ranger School is dealing with the sleep deprivation; I believe we averaged about three hours a night. Shorter periods — up to several days — of sleep deprivation are appropriate in training to mentally prepare soldiers for such a possibility in combat. However, the months of deprivation currently prescribed in Ranger School can degrade soldiers’ ability to consolidate memory, or learn, in the course.

Robert Angus and Ronald Heslegrave conducted a sleep-deprivation experiment that simulated a 54-hour military exercise. They found that performance on command-and-control duties (military-related cognitive tasks) decreased about 30 percent after the first sleepless night and 60 percent after the second night.

Independently, researchers June Pilcher and Allen Huffcutt found that loss of sleep hurts attention, working memory, executive function, logical reasoning, quantitative skills and motor dexterity. These are important areas for soldiers to retain what they learn in training.

Extended sleep deprivation also leads to health problems. Researchers found that rats deprived of sleep for 10 to 30 days lost temperature regulation, lost weight despite increased feeding, and eventually died. Scientist Anthony Fiorino reported a case of human insomnia leading to encephalitis, an inflammation of the brain, which became fatal. Meanwhile, in the case of fatal familial insomnia, loss of sleep invariably leads to death in a mean of 13 months. In 2009 researchers reported that prolonged sleep deprivation can inhibit hippocampal neurogenesis, endanger the brain structure and lead to mental disorders. Harvard neuroscientist L. Todd Rose has said that the two months of two to four hours of sleep per night at Ranger School most likely causes permanent atrophy in the soldiers’ hippocampi.

Taking this possibility of brain damage into consideration, further scientific research should be done on the effects of this practice to determine if sleep deprivation should be curtailed to benefit Rangers’ long-term health and to maximize the Army’s return on its investments.

Raising the stress threshold

Allostasis is the adaptive process for maintaining stability through change, such as unpredictable crises that threaten survival. As the allostatic load grows, stress becomes toxic and its demands overwhelm our psychological capacity to manage it.

A major determinant of allostatic load is the way an individual perceives a stimulus. What many people perceive as intensely stressful, others may view as a welcome challenge. While many soldiers fear being ambushed, most special operations soldiers develop a warrior ethos and are trained so extensively that they yearn for opportunities to employ their superior skills in a real firefight.

This highlights the possibility that we can raise soldiers’ stress threshold and reduce their allostatic load through training — in particular, through physical exercise and stress inoculation. Routine exercise is one thing that our military has done right to prepare our troops for the high stress of combat. Although commanders generally institute physical training purely for the physical benefits, exercise clearly has numerous psychological benefits, as well, stress-reduction not least among them.

Regular exercise reduces vulnerability to stress and the onset of stress-induced illness. It improves mood and cognitive function while reducing vulnerability to stress and depression. Numerous studies found that exercise reduces the excretion of stress hormones cortisol and epinephrine, while promoting the secretion of serotonin and dopamine, which counter the symptoms of depression. Meanwhile, studies showed that poor physical fitness is correlated to high allostatic load, lower cognition and cardiovascular disease.

Exercise also increases the creation of neurons and helps them resist and survive stress-induced damage. And it can improve synaptic plasticity, learning, memory and overall cognitive performance — all important for individual soldier tasks and leading military missions.

Furthermore, combat-focused physical training events, such as combatives (hand-to-hand combat) training and “stress-shoots” (a foot race integrated with shooting competitions in combat gear), also build the warrior ethos. This in itself can lower combat stress because it turns situations that most people would perceive as aversive into a welcomed challenge. This warrior ethos is cultivated well in Ranger School but could be improved in other training venues.

Stress inoculation

The other main area to explore is stress inoculation training, or SIT.

SIT is an individually tailored and multifaceted form of cognitive-behavioral therapy, which combines the cognitive emphasis on the role of thoughts influencing response and the behavioral emphasis on changing performance.

Studies have found that cognitive-behavioral therapy can help people reappraise stressful situations, increase activity in the medial prefrontal cortex, decrease activity of the amygdala and reduce blood pressure. In particular, cognitive-behavioral therapy has helped treat PTSD patients.

SIT was developed to “inoculate” people to specific stressors. University of Waterloo researcher Donald Meichenbaum cited 28 studies that support SIT effectiveness; Jens Gaab found that SIT reduces the neuroendocrine stress response in healthy young men. Men who received the SIT appraised stimulants as less stressful, displayed higher coping competence and had a reduced cortisol response compared with the control group. These findings suggest that stress inoculation training will attenuate soldiers’ combat stress response.

A military version of this could be employed to raise soldiers’ stress threshold for specific combat threats. Through numerous successful responses in training scenarios, soldiers would grow to perceive specific stressors as controllable, raise their threshold for the specific stressors and become closer to inoculated to the stress of combat.

SIT employs overlapping three phases. In the conceptualization phase, soldiers could be educated on the impact of stress and how to reappraise the enemy threats as challenges to overcome. In the skills acquisition and rehearsal phase, soldiers can learn to maintain composure under fire, take a moment to see the whole battlefield to assess courses of action, and then choose and direct the course of action with the greatest chance of success. This training and rehearsal could overcome the natural tendency to narrow attention in a threat situation. In the application and follow-through phase, training scenarios could be varied and the challenges increased so that soldiers experience myriad combat problems, including responding to ambush, reacting to roadside bombs and managing casualty evacuation under fire. To further consolidate these skills, soldiers could then train other soldiers (“train the trainer”) how to mindfully calm, assess, decide and lead in response to combat situations.

While many aspects of military SIT are incorporated into infantry and Ranger training, greater depth and repetition of specific and current-day combat training scenarios could enhance the entire Army.

The latest neuroscience research indicates that extended sleep deprivation and prolonged stress cause hippocampal atrophy and myriad health problems. Therefore, military training programs, such as Ranger School, that employ these practices should conduct comprehensive scientific reviews to determine if training practices should be revised. Depending upon those results, small adjustments in the training plan could further improve the school’s combat-preparation merit and enable Rangers to live longer, healthier lives. Research may indeed show that no training adjustments are necessary, but given the current scientific research ability, there should at least be that analysis and conversation between modern neuroscience and combat training programs.

Meanwhile, physical training and stress inoculation training in realistic combat scenarios, which raise soldiers’ stress threshold and prepare them to appropriately handle combat stress, should be sustained in Ranger School and conducted regularly by all units.

Daily moderate-to-intense physical training and weekly combat-focused physical training events should be continued in special operations and conducted by all military units to improve physical and mental health.

The combat training scenarios should continually evolve to represent current-day conflicts as realistically as possible. The more a soldier has handled a similar combat scenario in training, the less stressful the soldier will appraise the real scenario in combat, and the better the soldier will perform. For example, to best prepare soldiers for an ambush in an Afghanistan village, it would be best for soldiers to repeatedly train being ambushed in similar terrain and using the same vehicles.

Soldiers with inadequate training may become unnerved in direct combat, respond inappropriately, and will be at greater risk of attaining PTSD as a result. Therefore, military training should integrate the latest scientific research and continually be refined to give all of our deploying soldiers the best chance to succeed in combat and to return to a healthy life.

MAJ. STEPHEN C. FLANAGAN is an Army Special Forces officer studying psychology at Harvard’s Graduate School of Education and leadership at the Kennedy School of Government. He has completed four combat tours in Iraq and Afghanistan with the 75th Ranger Regiment and the 10th Special Forces Group. His next assignment will be teaching in the Behavioral Sciences and Leadership Department at the U.S. Military Academy. The views expressed in this article are those of the author and do not necessarily reflect the official policy or position of the Department of the Army, the Defense Department or the U.S. government.