by John Coates
Amines. A rhythmic alteration in the body between stress and rest, between the actions of anabolic and catabolic hormones, builds endurance. Some research has tentatively but tantalisingly suggested that such a regime may also expand the productive capacity of our amine-producing cells. These cells manufacture dopamine, noradrenalin and adrenalin, as well as many other chemicals, such as serotonin, the main target of antidepressant drugs such as Prozac. Amines switch on quickly, focus our attention, release glucose, and promote the full flight-or-fight response, just as cortisol does; but since the half life of amines in the blood is only a few minutes, they switch off as soon as the stress ends. According to Richard Dienstbier, one of the first scientists to work on toughness, a toughened individual is one who enjoys a powerful and immediate amine reaction when challenged, so he or she does not need to draw on the longer-acting and more potent cortisol response.
In a toughened individual, amine levels are lower at rest, rise more strongly when stressed, and shut off quickly. Since this person’s physiology is capable of handling the stressors being thrown at them, their homeostasis is not thrown out of balance, so they handle the stress without emotional distress. Physiological coping and emotional distress seem to be alternatives – if your body is coping, why get upset? As we saw when discussing homeostasis, emotions erupt, urging us to try alternative behaviours, when our body cannot handle a crisis on autopilot. The research into toughness has suggested that our brain silently compares the demands being made on us against the resources we can draw on (taking into account our training and skill). If our resources are sufficient we view the event as a challenge and relish it; if not we see it as a threat and shrink from it.
Our wonderful little amine-producing factories can, however, be overworked. Should our amine-producing cells be denied a rest period they become depleted; and then we are left to handle daily challenges without their energising influence. Depleted amines lead to a range of psychiatric and clinical disorders. Dwindling dopamine reserves, for example, can leave us lacking motivation. One of the symptoms of depression is a condition known as anhedonia, the failure to experience pleasure in life, any pleasure, even from favourite foods or activities; and anhedonia occurs with depleted dopamine cells. Similarly, depleted noradrenalin cells can leave us chronically lacking in arousal and enthusiasm. Worse, it can lead to the learned helplessness that Scott and Logan suffered. Such a condition can be brought on if we are exposed to unrelenting stress, such as combat, or divorce, or a two-year-long credit crisis, leaving us to brood over problems night and day, the troubling thoughts keeping the locus ceruleus on full alert, depriving it of any downtime, until eventually it is depleted of its precious noradrenalin. It is common among depressed people to have depleted noradrenalin and dopamine on the one hand, and chronically high levels of cortisol on the other.
What is remarkable about the research into toughening is the discovery that these amine-producing cells, like muscles, not only need a recovery period to rebuild their inventories, but can be trained to increase their productive capacity. The greater this capacity, the less likely they are to become depleted during stress, the more likely we are to view events as challenges, and the less likely we are to draw on the more damaging cortisol response. A strong first response by amines is the sign of someone who is coping; a strong cortisol response, someone who is not.
The picture of a toughened physiology that emerges from research on amines and hormones thus looks something like this: a toughened individual has a high ratio of anabolic to catabolic hormones. When faced by a challenge, the toughened individual experiences rapid and large increases in the amines, both in the brain and in the body, followed by moderate increases in cortisol. A toughened person, counter-intuitively, has a stronger initial stress response than an untoughened person, but he or she masters the situation, permitting the cortisol to abate, while the untoughened person mounts a weak arousal but the cortisol lingers, causing catabolic damage. Importantly, toughened people endure a sustained challenge without depleting the amines in their brain or succumbing to learned helplessness. Such a profile provides a person with all the cognitive and metabolic benefits of the amines while suppressing the damage done by a chronic exposure to cortisol. Such a profile is found, for example, in elite athletes.
It is also found in good traders. In one of the studies we conducted, I and my colleague found that the most experienced and profitable traders displayed extremely high and volatile steroid hormone levels, both testosterone and cortisol. The finding was initially puzzling, since we, like most people, expected veteran traders to be hardened and unemotional. And in fact they were, displaying little emotion through wins and losses. Nonetheless, behind their poker faces there roared an endocrine system on fire. In light of the research on toughened athletes, the finding makes perfect sense. Like Olympic athletes, these guys could call on their hormones when needed, and when the challenge had passed, the hormone levels rapidly returned to baseline before they could do any damage. Amateur traders, like amateur athletes, display the opposite profile: they have chronically raised cortisol levels, leaving them in a state of anxiety in which stressors come to be viewed as threats to be feared rather than challenges to be tackled.
The vagus nerve. We must now weave into the fabric of a toughened physiology the role played by the rest-and-digest nervous system, and the vagus nerve in particular. The fight-or-flight nervous system prepares us for vigorous, even violent action, but the rest-and-digest system takes over once the action has finished. It is, to extend Shakespeare’s apt phrase, ‘great nature’s second course’, and together with anabolic hormones it knits up the body’s ‘ravell’d sleeve of care’.
The calming effects of the vagus have led Stephen Porges to view it as a highly evolved and efficient tool for conserving energy. Porges has traced the history of the vagus nerve and found that as it evolved from its simplest state in reptiles to its more complex form in mammals, it played a role in three successive stress responses: freezing, fight-or-flight, and social engagement. Porges’s history is worth recounting because it suggests that the advanced vagus nerve we have inherited today may provide us with one of our most valuable resources for minimising the ravages of stress.
In reptiles, the vagus orchestrates a primitive reaction to threat – freezing into a motionless state. Reptiles freeze in order to conserve their limited energy and avoid detection. This freeze response was subsequently passed on to mammals, in which it proved useful as a way of feigning death when a threat loomed. Something like the freeze response is also activated in mammals living or feeding in water, such as seals, in order to slow heart rate and metabolism and conserve oxygen when diving to great depths. The vagal freezing response lingers to this day in most mammals, and can show up under circumstances of extreme danger. When escape from a predator is deemed impossible, a mammal can call on this ancient reaction, and its physiological systems will more or less shut down. Movement ceases, breathing slows, heart rate drops, sensitivity to pain decreases – pathetically, the animal may provoke cardiac arrest and die from its own reaction to threat rather than from the predator itself. Something like this phenomenon has been observed in wild rodents trapped in water they fear they cannot escape. These poor animals, realising the futility of struggle, frequently opt for freezing and cardiac arrest, some of them even diving into the depths, drowning themselves. Presumably they do so to trigger a dive-induced freezing, leading to a rapid and painless death.
We humans retain this prehistoric freeze reaction. You can verify this fact by dipping your face into cold water (only your face will do), for this action triggers the dive reflex, which slows the heart rate and breathing, and quite possibly gives you a shot of natural painkillers. When highly stressed, people often splash cold water on their faces to engage this reaction, even if they have no knowledge of the physiology involved. Vagal freezing may also show up, some scientists have suggested, in cases of sudden death caused by the receipt of shocking news, and
even in documented cases of voodoo death, an inexplicable death brought on, presumably, by the complete conviction held by a person that the curse just placed on them will prove effective.
In the next stage in the evolution of the vagus, this nerve came to cooperate with the fight-or-flight response. During fight-or-flight the vagus removes its slowing influence, what Porges calls the vagal brake, from visceral organs so that fight-or-flight can take over, just as it did when Martin and Gwen heard the Fed announcement and launched into action.
It is in the third stage of its evolution that the vagus nerve reaches its most sophisticated and encouraging form – as a tool of approach and conciliation. Porges sees the human vagus as a system of social engagement, an evolutionarily advanced and metabolically efficient alternative to fight-or-flight that promotes diplomacy instead of confrontation. Speaking in a calm and reassuring voice, making eye contact, displaying facial expressions that broadcast cooperation rather than confrontation, all these help avoid a metabolically expensive and potentially damaging fight; and crucially they calm our visceral arousal. The vagus nerve, it could be said, forms the diplomatic core of the body.
Today we harbour within our bodies all three vagal reactions. Each of these may be initiated when we are caught in an escalating confrontation, beginning with the most recently evolved one, and then proceeding to the older ones. Our first reaction to a challenge is accordingly social engagement, in other words, talking, making eye contact, calming down the situation. If this diplomacy fails then we reluctantly fall back on the older fight-or-flight reaction. Should even this fail and neither victory nor escape from the threat proves possible, then we may lapse into the ancient reptilian state of freezing or giving up or feigning death or in extreme and very rare cases dying a voodoo death. In the course of this confrontation we have regressed millions of years in evolutionary time.
Our highly advanced vagus nerve permits us to subtly adjust our stress response to the demands made on us. By doing so, it conserves energy. When confronted by daily stressors the vagus merely eases off its brake, permitting our body’s idle to speed up just enough so that we can handle mundane challenges without bringing online the more costly fight-or-flight or cortisol systems. This may be one reason that people who view an unexpected event as a challenge have been found to display efficient cardiac output coupled with low blood pressure in their peripheral arteries; while people who view the event as a threat have inefficient cardiac output and high blood pressure. Indeed, people who lack a well-functioning vagus, who suffer from what Porges calls poor vagal tone, tend to overreact to mild stressors, and instead of calibrating a subtle response to these mundane situations they launch into a full fight-or-flight confrontation. Uproar is their only music. The lack of good vagal tone drains a person’s energy and ultimately their health. Porges has found that children with low vagal tone display more behavioural problems later in life.
On the other hand, truly toughened individuals, the physiological elite, such as world-class athletes, may have been gifted with bodies and brains so primed for maximal effort that they appear almost otherworldly in their ability to cruise through a gruelling physical contest with nothing more than a slight release of their vagal brake. Can they really be performing that well just on their body’s idle speed?
Vagal tone can be measured through a person’s heart-rate variability. When you breathe in, your heart rate speeds up; when you breathe out, it slows down. This speeding up and slowing down is governed by the vagus nerve. People with good vagal tone will have heart rates that are highly variable. This variability is a good thing – the slowing down giving our hearts what amounts to a mini-rest every breath – and has been correlated with a number of markers of health. (It should not be confused with palpitations or heart arrhythmias – these are irregular heartbeats, but not ones that occur systematically across every breath.) On the other hand, people with poor vagal tone, or people who are stressed, will show little or no heart-rate variability, their hearts pumping at a constant rate. This lack of heart-rate variability is a risk factor for hypertension and future heart disease. Heart-rate variability can be monitored easily with a small device, sold commercially, worn on your chest or clipped to a finger.
We can therefore add good vagal tone and a high level of heart-rate variability to our profile of a toughened individual. In fact, one study of soldiers has found that a high level of heart-rate variability generally co-existed with a high ratio of anabolic to catabolic hormones.
In short, a toughened individual, one who views novel events as a challenge to embrace, draws on very different physiological systems from an individual who views them as a threat to avoid. Their different responses could be described as offence versus defence. The former is energising and enjoyable, leading to the coveted state of flow; the latter is draining and unpleasant, leading to a fear of the world.
Incidentally, the dramatically different physiological experiences of challenge and threat may be an underappreciated influence in social confrontations such as legal disputes and political battles. Take the example of a group of villagers fighting a developer in order to preserve their green spaces, or the managers of a company facing a hostile takeover. These people are confronted by developers and takeover sharks who live for such battles, revel in them. But not the defenders. For them the battle is a desperate and unpleasant experience, soaked in stress hormones, and it leaves nasty memories that may dissuade them from getting involved in future confrontations. It is often said that in war the best defence is a good offence; and perhaps in politics, business and sport, there is physiological support for this bellicose piece of advice.
THE SCIENCE OF GRACE UNDER PRESSURE
Can we toughen our physiology? Inevitably, a good deal of our toughness comes from the genes we inherit. Certain genes, for example, make some people more immune to the effects of stress and the stress hormones. But some scientists have found that developmental influences affect the way a person handles stress later in life. They have found that acute stress, in other words short-lived and moderate stressors, early in life can toughen an animal for adulthood. Young rats that are handled by humans will develop larger adrenal glands, but nonetheless as adults will show a more muted stress response to threats. They also tend to live longer, one study finding a life expectancy18 per cent longer than that of non-stressed rats. The acute stressors must, however, be acute and moderate, for the same research showed that major stressors early in life, such as maternal separation, foster an anxious adult ill-prepared to deal with the slings and arrows of normal life events.
The training or toughening effects of acute intermittent stress can also be observed in adult rats. These stressors may include handling by humans, running on an exercise wheel, mild shock, even having their amines depleted by drugs. It does not seem to matter that much what the stressor is. The stress response is a general, bodywide reaction, so any stressor can exercise it. Each of these stressors, if brief and repeated, could toughen the rats. Call it the school of hard knocks.
What stressors could contribute to toughening in humans? Research on toughening regimes is still in its infancy, but a few types of stressors nonetheless crop up in the literature. The most important, not surprisingly, is exercise. Humans are built to move, so move we should. The more research emerges on physical exercise, the more we find that its benefits extend far beyond our muscles and cardiovascular systems. Exercise expands the productive capacity of our amine-producing cells, helping to inoculate us against anxiety, stress, depression and learned helplessness. It also floods our brains with what are called growth factors, and these keep existing neurons young and new neurons growing – some scientists call these growth factors ‘brain fertiliser’ – so our brains are strengthened against stress and ageing. A well-designed regime of physical exercise can be a boot camp for the brain. In the future, however, the advice to exercise, administered so liberally by doctors everywhere, could be made more effective by being more explicit. What t
ype of exercise? Anabolic or anaerobic? How often? Once again, sports science could help enormously in tailoring this advice to the person receiving it.
One type of toughening regime is especially intriguing, and that is exposure to cold weather, even to cold water. Scientists have found that rats swimming regularly in cold water develop the capacity to mount a quick and powerful arousal, relying on adrenalin more than cortisol, and to switch it off just as quickly. When subsequently exposed to stressors they are not as prone to learned helplessness. Some tentative research has suggested that much the same thing occurs in humans. People who are regularly exposed to cold weather or who swim in cool water may have undergone an effective toughening regime that has made them more emotionally stable when confronted by prolonged stress. It is surmised by some researchers that the exercise itself, coupled with acute thermal demands, provides these people with an enviable pattern of stress and recovery. Perhaps the same effects could result from the Nordic practice of a sauna followed by a cold plunge.
Recall that thermoregulation represented a revolutionary advance for mammals, profoundly altering their bodies, brains, and the network of connections between the two; and that it proved particularly so for early humans, whose superior ability to cool their bodies gave them an edge on the African savannah. Some scientists have even claimed that the nervous system supporting thermoregulation in mammals laid the foundation for later systems of emotional arousal. Dienstbier has elaborated this idea, and argues that people who have developed cold tolerance may also have increased their emotional stability.