When Schaffner explored the historic literature, however, she found that people suffered from extreme fatigue long before the rise of the modern workplace. One of the earliest discussions of exhaustion was written by the Roman physician Galen. Like Hippocrates, he believed that all physical and mental ailments could be traced to the relative balance of the four humours – blood, yellow bile, black bile and phlegm. A build-up of black bile, he said, slowed the body’s circulation and clogged up the brain’s pathways, bringing about lethargy, torpor, weariness, sluggishness and melancholy. Although we now know it has no scientific basis, the idea that our brains are filled with a tar-like liquid certainly captures the foggy, clouded thinking that many people with exhaustion report today.

By the time Christianity had taken hold of Western culture, exhaustion was seen as a sign of spiritual weakness. Schaffner points to the writing of Evagrius Ponticus in the 4th Century, which described the ‘noonday demon’, for instance, that leads the monk to stare listlessly out of the window. “It was very much seen as a lack of faith and a lack of willpower – the spirit versus the flesh,” says Schaffner. She points out that one monk reported compulsively and restlessly seeking out his brethren for idle chit-chat rather than engaging in useful employment – in much the same way that 21st-century sufferers may find themselves compulsively checking social media.

Religious and astrological explanations continued to abound until the birth of modern medicine, when doctors began diagnosing symptoms of fatigue as ‘neurasthenia’. Physicians now understood nerves transmitted electrical signals, and they believed that someone with weak nerves may therefore dissipate energy like a badly insulated wire. Intellectual figures from Oscar Wilde to Charles Darwin, Thomas Mann and Virginia Woolf were all diagnosed with neurasthenia. Doctors blamed it on the social changes of the industrial revolution, although delicate nerves were also seen as a sign of refinement and intelligence – some patients languished with pride in their condition.

Although few countries tend to diagnosis neurasthenia today, the term is often used by doctors in China and Japan – again, with the occasional accusation that it is an alternative, stigma-free way of labelling depression.