Of all the hormones, cortisol is the one most of us believe we have sussed. It’s evil, right? It sweeps through the body when we are stressed and it ravages us. Don’t leave that child to cry, don’t stress that toddler out, don’t manage behaviour like this or like that, don’t force exams on helpless teens, sort workload out for teachers - because, you know, cortisol.

“Everyone wants cortisol to be the bad guy and thinks that high levels are problematic,” sighs Emma K Adam, professor of human development and social policy faculty fellow at Northwestern University’s Institute for Policy Research in Illinois, US.

The reality is that it is a little more complicated than that.

“A lot of people call it a ‘stress hormone’, but that is only one of the things that it does,” explains Adam. “While it is released in response to stress - so [levels] will go up when you encounter a stressor - cortisol also has a daily rhythm that is very important for basic maintenance of energy levels, metabolism, immune-system functioning and other things.”

She adds that an increase in response to stress is not always a bad thing. In fact, it can be beneficial.

Cortisol can be a villain - and a potent one. But it is also a cog in our biological clock, a motivational push in the right direction and a support system for when we are in trouble. A better understanding of it might influence not just how we view stress in schools, but also how we can structure educational provision so that the negative side of the hormone can be kept at bay.

Conducting the orchestra

Let’s start with the basics. The rise and fall of cortisol levels is entirely normal. Everyone has a daily cortisol “rhythm”. Typically, the level in the body begins to increase in the morning as it gets light; there is a “surge” for about 30 minutes just after waking; and then it tends to gradually decline as it gets dark outside and the body prepares for sleep.

This 24-hour cycle, part of the circadian (or biobehavioural) rhythm, does not usually develop until a child is about 18 months old. If you measure young children’s cortisol when they are crying, feeding or sleeping, the levels can vary widely. These variations become less pronounced the older we get.

As University of Westminster emeritus professor Angela Clow explains, keeping our natural rhythms regular is cortisol’s main job. “The first and fundamental thing that people should understand is that its first role is to regulate 24-hour cycles,” she states. “It’s a master hormone - like the conductor of an orchestra.”

If our cortisol levels change appropriately, then the day should run harmoniously. When we wake up in the morning, the normal cortisol surge will help get us going, overcome our sleepiness and face the demands of the day. At night, cortisol levels will be lower and we will sleep more easily.

Sleep, of course, is integral to being healthy. For example, it can affect the immune system, energy levels and metabolism - and it is crucial for learning, too. We therefore owe cortisol a great deal of debt.

But cortisol has another job, too - the one it has become best known for: helping us respond to stress.

This secondary role is widely misunderstood. It is commonly thought that cortisol is the trigger for the fight-or-flight response; it is not. If you are stressed out by something, you may get a bit sweaty, or your blood pressure or heart rate may rise, as your first reaction. Those immediate changes are not mediated by cortisol, but by adrenaline.

Cortisol is much more concerned with sustaining the stress response if the stressor remains. It is, if you like, the second-wave response (see bit.ly/StressResponse2).

People also assume that high levels of cortisol are always bad for you. We are told not to let our children cry for longer than set time limits; not to put undue stress on young people lest their cortisol levels increase; not to make sport competitive, to lessen the stress surrounding the end result.

Actually, deviations from the “normal” cortisol cycle of highs and lows are not necessarily bad. In fact, they can be quite the opposite. On the day of a big exam, cortisol levels may be marginally higher; similarly, levels will spike in response to something unexpected and shocking - perhaps a realisation that homework has been forgotten, or a run-in with a bully. This is normal and can improve your ability to deal with the stressor you are facing, making you more alert or giving you more energy. After all, that is what it is designed to do.

“Cortisol is not a bad hormone. It’s essential for life,” insists Clow.

So why all the flashing warning signs? Well, because it does indeed have a dark side.

Cortisol is at its most dangerous when significant deviations from normal levels become the norm.

“The problem with things that are essential is that you have got to get into the ‘Goldilocks zone’; either too little or too much is really bad for you,” says Clow.

Exposure to chronic stress resulting in the repeated heightening of cortisol levels, in particular, can be devastating. Clow describes it as being like a “dripping tap”: slowly, over a matter of years, the body becomes dysregulated, the receptors for cortisol become desensitised and then “this lovely dynamic of waking and sleeping becomes flattened - it is like the conductor of the orchestra is not conducting properly”.

She gives the example of a teacher she studied as part of a television series. “We monitored him for a normal teaching day and, my word, he was off the scale in cortisol,” she recalls. “As soon as he got home, it went right down, and when I measured him at the weekend, he was absolutely spot-on healthy.

“But my prediction would be that if he kept doing that, month upon month, year upon year, in the end, the resilience goes and the dysregulation will kick in so that even at the weekend, when he is not exposed to these stressors, he is going to show this cycle.”

The detrimental health effects of sustained high (or, indeed, low) levels of cortisol are numerous - including impairment to learning, according to studies, and even fatal conditions.

Staying tuned in to stress

Keeping both pupils and staff away from the dangerous, flatter cortisol cycles, where the hormone’s levels are too high or low, and instead being able to intervene or structure education to help keep them in the “Goldilocks zone” (in which reactions to stressors are “normal”), is not a simple process.

There are some identifiable risk factors we can look for, according to Clow. For example, social disadvantage is strongly associated with chronic stress.

“Stress is linked to the way you live,” she explains. “Crowded housing, a noisy environment, no space, a less healthy diet [can all contribute to stress]. It is not a level playing field.”

Adam agrees: “An unhappy home life [can push cortisol levels up]. Poverty, exposure to racial discrimination, bullying - cortisol is super-responsive to social rejection or exclusion of any form.”

The impact of trauma can be significant, too, as explored in a recent Tes Podagogy podcast (bit.ly/TraumaBehaviour).

But every individual is different. While stressors can be common (big exams, for example), some may be highly individualised: one pupil’s stress is another’s walk in the park. For some, a walk in the park might be stressful. It’s a difficult one to judge.

And we would also have to be careful to distinguish between normal stress reactions and more dangerous, persistent stress.

So how useful is it for teachers and school leaders to know more about cortisol? Well, it can at least inform how we view stress and influence how we construct educational provision to minimise the chance of chronic, long-term stress.

For starters, we need to be careful not to overmedicalise what are normal reactions to stressful events: an increase in stress, and thus cortisol levels, in response to an exam is, as explained earlier, entirely normal. If we warn children or teachers that stress is bad for them and try and prevent any form of it, we risk causing more worry unnecessarily, restricting experiences or opportunities and providing inaccurate information.

The research on cortisol offers yet another indicator of just how important relationships are in education, too. Knowing our pupils (or, as a leader, our staff) well allows us to begin to understand what they find stressful. It can give us an insight into the person beyond the data sheets and help us better understand the context. Regular meetings would allow us to spot changes in behaviour. All of this should mean that we would be able to better identify when the “normal” stress reactions set out above become chronic and dangerous.

In addition, the internet is awash with techniques to de-stress; the evidence for the positive effect of mindfulness is well established for adults, while it is also growing for children.

No nasty surprises

But there are also structural and environmental things specific to schools that we can do, too. Exams are a good example.

“What you want in a testing situation is moderate cortisol levels,” states Adam. “If you are super-stressed out and worried - so if the test is a threat to you - your cortisol levels can get to the point of being too high and they can impair your performance. But if you are not even engaging with the test and you are not getting any cortisol increase, then you tend to be fatigued and disengaged.”

How we approach exams in school can be a big factor in whether a pupil is in the “Goldilocks zone” of cortisol’s positive impact, the danger zone of a very high spike or low dip before an exam, or has persistently high levels in the months leading up to exams.

“I would say making sure kids know that they are valued aside from test performance is important,” Adam says. “Also, kids pick up on teachers’ nerves, so if teachers can control how stressed out they are getting about the test, that would help the kids perform better.”

What could also help, she claims, would be a policy change: the spreading out of assessments over a longer period of time rather than placing an emphasis on one exam period.

“The more high-stakes the test is, and the more likely their futures depend on it, the more likely it is that you might see students performing worse,” she argues.

Away from exams, Ian Goodyer, a child and adolescent psychiatrist based at the University of Cambridge who researches the connections between human development and psychopathology, says that predictability can be key.

“If you’re a student and you walk in through the school gates and someone clobbers you with a cricket bat, your cortisol will go up. If you’re that same student and you walk into the classroom and suddenly discover you’ve got the worst mark in the class for something you did, your cortisol will go up, too,” he says. “People need to be communicated with and planned [with]. They need to prepare for what’s around the corner. I think the use of performance measures that involve a surprise element, as if somehow you’re getting prepared to fight the enemy, is nonsense.

“If we want young people to lay down the right memories and experiences, they need planned, predictable, supportive and rewarding environments.”

That may mean having a very structured environment with clear rules, boundaries and routines. But equally, it can mean just making sure the pupils are communicated with regularly and are kept informed of changes and the boundaries within which variation may occur. It is about providing a heads-up prior to results or feedback so there is no continual run of surprises that spike stress reactions.

For teachers, the same advice is applicable. What can help here is more notice of observations, more routine in performance-feedback procedures, and better communication and planning from leaders.

Finally, Goodyer says that there is one thing every school can do to help people mitigate the impact of stress - one that should be on every teacher’s list anyway: providing amazing experiences. “If you’ve got good memories, you can actually lower your cortisol - literally by thinking about good things,” he says.

The more happy memories created, the better equipped we are to deal with stress.

In short, he concludes, we need to help people “go to their happy place”.

Chris Parr is a freelance writer

This article originally appeared in the 8 March 2019 issue under the headline “Cortisol: not the baddie you might have thought”