Can stress ever be beneficial?

Why do civil engineers spend trillions of dollars building bends into roads when a straight one would do just fine? Why has the number of prescriptions for anti-depressants almost doubled in the past decade? Why do some people perform better under stress? According to Professor Ian Robertson, the answer to all these questions has a lot to do with noradrenaline – 'a potential candidate for the most remarkable brain enhancing substance'.

Robertson has worked as a clinical neuropsychologist, and written numerous popular and academic books. His latest, The Stress Test, surprised him: 'I didn't realise how relevant what I had been studying was to this whole realm of stress and psychological injury.'

Robertson's big idea is that how the brain responds to pressure can sometimes push the brain into a 'sweet spot'. Increasing the challenge a person faces allows the brain networks to communicate better. 'A bit of stress, not too much, is good for you.' Perhaps more importantly, how we reframe stress – as a challenge – can have major impacts on our physical and mental health.

Clearly influenced by his time at the Institute of Psychiatry. Robertson describes it as 'a wonderful institution,' he says, 'but one with a split personality. There were practitioners, and scientists doing basic research. There was almost no interaction between the two, and that continues to this day. I know which side really won.'

Robertson clearly longs to join the dots, in an age of an 'epidemic of the emotional disorders of life'. 'Depression is a ghastly thing to suffer from, particularly against all the other improvements in physical health.' In an age where everyone bangs on about dopamine, Robertson has another focus: 'I'm very interested in noradrenaline as a neurotransmitter – some say it's because it's the only one I can pronounce.' 

Why noradrenaline? According to Robertson, it integrates working memory, arousal, awareness and sustained attention. It's key to a fundamental, 100-year old law in psychology, the Yerkes-Dodson law. Fundamentally, it's when 'thoughts, perceptions, actions, are beautifully represented because there's just the right amount of background noise.' If you're low on the curve, stress or challenge pushes you into the sweet spot – happy days. If you're already there, it's only downhill.

Imagine you're really anxious about doing maths. You're actually as good as it as everyone else, you're just extra anxious about it. Then you're put in front of a 'censorious audience' (I don't like them already). According to 2011 research by Mattarella-Micke and colleagues, those who are high in maths anxiety do worse when they secrete more cortisol (a notorious stress hormone). But those low in maths anxiety actually do better – the stress, or challenge, boosts their performance.

What's going on here? Robertson says the high maths anxiety students are 'already up here' – more stress simply pushes them over into a negative relationship between cortisol and performance. But the low maths anxiety students are pushed up into the sweet spot.

What drives this? According to Robertson, it's sustained attention, strongly linked to noradrenaline. The challenge for the brain is to keep itself internally focused when there's not much in the way of external drivers. We all wander a little, but Dan Gilbert's work has suggested that a wandering mind is an unhappy mind. Even if his participants were doing a boring household chore, if their mind was wandering their mood was lower – and the paper showed that link was causal. 

Robertson measures this sustained attention with his simple 'SART' test – just press the button for every number except 3. 'Strangely enough', he says, 'people make errors'. It's a highly specific and sensitive test for people with traumatic brain injury, but perhaps more interestingly it predicts real life cognitive failures and absent mindedness in everyone. And when one of Robertson's colleagues had used it in New Zealand before the Christchurch earthquake, an opportunity presented itself to create an 'Earthquake Induced Cognitive Disruption Scale'. Performance on the test of sustained attention highly correlated with the likelihood of people experiencing stress symptoms related to the earthquake. 'Stress is a gateway to our emotional life', said Robertson. 'If you let your mind wander, it will tend to wander to negative thoughts and memories. Why? Because the brain hates unresolved conflicts.'

So, back to those straight roads. 'There's one in Kuwait,' Robertson says: 'you just see burnt out wrecks along the way.' Why? Because the brain needs challenge to sustain attention in the absence of external demands. And this has interesting implications for the tests neuropsychologists use. 'Many of our tests automatically switch on this situation. They challenge, they "help out" the person unwittingly.' Robertson referred to more unstructured tests, for example the 'six elements' test from Tim Shallice and Paul Burgess, that is more unstructured and doesn't obviously involve challenge. Using Tom Manly's real life test based on things hotel receptionists would need to do, Robertson showed that the simple act of ringing a buzzer randomly when you give the task to brain injured patients can normalise performance. 'It's pushing them up to the sweet spot.' [O'Connor, Robertson and Levine, in Neuropsychology.]

Never straying far from noradrenaline, Robertson showed that SART errors can be predicted according to which copies you hold of the DBH allele which affects the presence of noradrenaline in the brain. And when you 'up regulate' noradrenaline with a drug, it activates the frontal and parietal cortex in the right hemisphere: 'the key to keeping your mind internally directed'. Luckily, you can even measure this noradrenaline activity via pupil dilation. 

This is where it gets a bit weird. Clever people, their pupils dilate more in response to a difficult problem. They're generating more noradrenaline. 'People with above average IQ,' Robertson says, 'are constantly infusing their brains with a remarkable drug which has amazing effects in the right quantities. Engaging in challenging activities generates this incredibly enriching substance.'

So that's why stress can be good. Animal research shows that rich, complicated environments grow the brains of many animals. And it's not just complexity, it's the novelty. One new smell every day for 40 days produces neurogenesis in mice. Yet if you block noradrenaline, you lose that effect. 'There's three sisters,' says Robertson: 'rich and complex environments, mediated by novelty, in turn mediated by noradrenaline.'

The implications of this are mind blowing. If you're smart, this lifetime of boosted noradrenaline activity may affect the disease process itself, protecting the brain from the ravages of time. 'Take Vietnam vets', said Robertson – 'the best predictor of their adaptation to brain injury was the brain that existed beforehand.'

So we're back to the neuropsychological patients Robertson has spent so much of his career with. Considering the psychological legacy of the Battle of the Somme, Robertson showed a photo of a casualty: 'He's been through the far side of the sun… There should be no holds barred in the methods available to him. There's no easy psychological fix, but doesn't mean you can't contribute.'

And the way psychologists can contribute is surprisingly simple. If the key is sustained arousal, why not train people to give themselves little jolts of arousal? Using adults with attention deficit problems, Robertson and colleagues used skin conductance biofeedback. 'We literally just clapped hands behind their head, showed them how their skin conductance changed and told them to do it themselves.' The team were changing brain chemistry, and linking it to real life problems.

Moving back to stress, Robertson covered 2011 research by Hannie and Comijis suggesting that 'cognitively fragile' older people who had no significant life events in a two-year period were poor on a retention test, but those who had three more life events in the moderate range were just as good. 'Moderate stressors jizzed up their brains,' said Robertson, wheeling out all the technical terms… 'almost certainly by pushing them up to the sweet spot.' 

But it's not just in older people. Research by Mark D. Seery suggests that cumulative life adversity can have a powerful beneficial effect in the face of chronic back pain. 'The lesson here,' Robertson concluded, 'is that people need to toughen up a bit.'

Talking of which, what does all this mean for that 'epidemic' of anti-depressant use? Robertson, admittedly riffing more speculatively on this theme now, laid the blame on youths being 'over-sheltered from adversity', and lacking experience in 'tolerating and controlling negative emotions – particularly through attention and mislabelling of arousal.' As a result, people don't feel in control of their negative emotions. This, Robertson argues, is particularly pernicious. Drawing on Carol Dweck's ideas, he suggested that the medicalisation of mental processes has led to a fixed rather than growth mindset. Does being given a pill for your psychological state convey a powerful message that you are not in control of your emotions?

According to Robertson, 'we do have control over our biological factors' (although he qualifies that with 'to some extent, in some cases'. The scientific reality is that we should have a growth mindset about all our processes. 'The brain is so plastic, the capacity so profound. It's terrible that people don't feel they have that.' 

So how do we change a mindset? 'We live in a society with a tendency towards reductionism,' Robertson concluded. 'But there's going to be the kind of kickback that happened with the mass prescribing of Valium.' Where America leads, the world follows, Robertson suggested, and 'the Trump supporters, they're dying' – through suicide, alcohol misuse, and the huge issue of prescription painkiller use. As psychologists, Robertson concluded, we need to assess different things – arousal, self-awarness, insight. But perhaps more than anything, we need 'that little rewriting of the software code' – from potentially harmful 'stress', to beneficial 'challenge'.