Why not knowing is stressful
Have you ever waited for someone to call you with important news? Maybe it was an exam result, the outcome of a job interview or, worse, a call from the hospital. The reason that waiting for important news produces anxiety is that brains are pattern detectors that have evolved to seek out regularities in life; not being able to predict what will happen next is therefore upsetting. We can brace ourselves for important events, but it is stressful to maintain that level of preparedness for a long time. The stress comes from high levels of arousal – a state of readiness and expectation. Just like the US Army, when we face a threat, we enter a defence-readiness condition (DEFCON). When that threat is at a peak, it’s like being at DEFCON 1. This is why we jump at the slightest sound, because we are in a state of heightened alertness. It is not until we can stand down our defences that we can relax.
Even though we may not be actively dealing with a threat, nevertheless the uncertainty of threat still makes the situation stressful. In fact, our brains are not very good at dealing with random events, which is why we tend to see structure and order everywhere. That is why when you are in the woods late at night or an old spooky house, every noise sounds like a threat. Adults start to see patterns in random noise when you remove their ability to control outcomes or remind them of times when they were helpless.19
This lack of control is not only psychologically distressing, but it also affects how our bodies respond. Even our tolerance to pain is reduced. Adults can withstand much more painful electric shocks if they think they can stop the punishment at any point in comparison to those who do not think they have this option.20 Believing you can stop the pain whenever you want means that you can tolerate more. However, when faced with unpredictable and uncontrollable shock, both animals and humans develop both psychological and physiological illness.
This need for control and predictability is present from the very start. Babies prefer regularity and predictability, which is why they startle to sudden unpredictable noises, lights or movement. In fact, there is a reflex controlled by the brain stem – the most primitive part of the brain that controls vital functions – known as the startle reflex, that jolts the child to attention. If a newborn does not startle, there is a chance that they have some form of damage to their nervous system. This need for predictability forms the basis for contingent behaviour where the baby starts to learn how they are synchronized with others. Such a sensitivity to external events means that a nurturing domestic environment is one that is going to be predictable and less threatening – attributes that can be controlled by caregivers.
Infants thrive on predictable contingent behaviour, but the flipside is that they find unpredictable or non-contingent events upsetting, especially when they involve their mother. When mothers are depressed, they often have flattened emotions and so the quality of their interaction with their infants is impoverished.21 Other depressed mothers, rather than being sad and dull, over-compensate in an animated, exaggerated form of communication, which can be equally distressing to the infant because it is not contingent with their own efforts at communication. Early experiences like this, where the baby’s needs for contingent responses are not met, can lead to social and cognitive difficulties many years later.
Other people provide reassurance in an uncertain world. The stress of uncertainty is reduced if there is an adult around, so our brain benefits not only from the wisdom of others but their presence as well. As the saying goes, a problem shared is a problem halved because there is strength in numbers. If you think about it, the world is full of surprises for the young infant and development must include discovering what is going to happen next. With knowledge and experience, the world becomes more predictable. That understanding takes time to acquire, but until then, adults provide protection and reassurance, which is why babies cry if there is uncertainty because it is how they signal to the adult to resolve the situation.
Taken together, these studies indicate that extreme early environments can have long-term effects on developing monkeys and humans. It would seem that primates need some form of contact from the very start, especially in environments that are particularly threatening or socially vacant. However, it is not just the deprivation of not having others around, but not having others around who are reliable. How do such stressful environments shape who we become and what role do others play in our reaction to stress?
Learning to fight or flee
To understand how aversive unpredictable environments affect growing brains, we need to understand the normal response mechanisms to stress. When faced with a threat, we can either stand up to it or run away. There is a rapid fight-or-flight response where we get that sudden emotional rush that requires us to mobilize as quickly as possible that is triggered by activity in the limbic system of the brain. This preparedness is achieved by a system called the hypothalamic-pituitary-adrenal (HPA) axis.
Following exposure to stress, the hypothalamus releases two hormones, corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP), that stimulate the nearby pituitary gland to release adrenocorticotrophic hormone (ACTH) into the blood stream. ACTH targets the adrenal glands that sit atop the kidneys way down in the guts to release adrenaline, noradrenaline and cortisol. The balance of adrenaline and noradrenaline regulates the autonomic nervous system (ANS), which in turn increases breathing, heart rate, sweating and pupil dilation, and shuts down digestion. After all, you don’t have time to chew the cud when you are about to do battle. If you have ever felt butterflies in your stomach before going on stage, that was your ANS operating. Cortisol works by increasing the concentration of glucose in the bloodstream, thereby making more fuel available for muscles. All of this activity is fine when there is a real threat that needs to be dealt with immediately. However, the fight-or-flight response has to be wielded appropriately and used in moderation.
Figure 6: The hypothalamic-pituitary-adrenal (HPA) axis
Maintaining high levels of stress over long periods leads to chronic impairment in our ability to cope with life’s ups and downs. It is like keeping your foot on the accelerator pedal, revving the engine, and it will eventually cause damage to the HPA axis mechanisms and subsequent illness and impairment of your immune system. Chronic stress has also been linked to psychiatric disorders such as depression, with most individuals suffering from major depression having increased HPA activity.22 So, to keep body and mind in a healthy state, you need to be able to regulate your stress response. Part of this regulation is provided by the hippocampus. Within the hippocampus, there are glucocorticoid receptors (GR) that monitor levels of glucose and cortisol in the bloodstream. When levels of circulating glucose and cortisol reach a critical level, the hippocampus signals the hypothalamus to shut down the HPA process in the same way that a thermostat on a heater regulates temperature. If a thermostat is faulty, the house freezes or overheats. Likewise, if the HPA is disrupted, either you do not respond adequately to stress or you overreact.