Sleep is an urgent topic for the twenty-first century, but fretting about sleep also has a much longer history. Sleep, we all know, is a good thing: we need it, we appreciate it, it sustains us. When we think about sleep, it is usually in terms of wanting more of it, thanks to the complications of modern life: alongside age-old adversaries of restful sleep such as illness, alcohol and caring responsibilities, modern factors such as high stress levels, shift work, jet lag, caffeine, screen time and non-natural light have all dramatically deepened our collective societal sleep debt. In the sleep stakes, industrialisaton has a lot to answer for; since the early twentieth century, people have been sleeping increasingly less. Popular science books addressing sleep have proliferated in recent years, focusing on how to sleep most effectively, and how to get the most from your sleep, whether at night or during a day-time nap. Yet, partly due to the availability and prevalence of electric light and stimulants, the 24/7 modern culture has prioritised constant productivity and alertness at the cost of sleep, despite growing awareness of the benefits of sleep for physical and mental health.
We are, as it were, waking up to the urgency of getting enough sleep, and even the productivity paradigm has shifted to adduce the benefits of sleep. Some sleep experts are seeking to debunk ‘the myth that presenteeism and productivity are the same thing’, in ways that might help to counter the insidious expectations of expanding workloads. At a time when some sleep scientists, along with the World Health Organisation (WHO), have stated that all industrialised countries are living through a potentially catastrophic ‘sleep loss epidemic’, what can we gain by turning to the ways in which people thought about, and performed, sleep in the past?
In late medieval and early modern England, sleep was widely understood to be necessary and beneficial, and its benefits – both physiological and psychological – originated in sleep’s vital role in digestion. Galenic medical tracts urged the importance of sleeping in the right ways and at the right times. Galen (129-c.210 CE) was educated in Alexandria, and his medical learning included the works of Hippocrates and Aristotle; Galen’s influential medical tracts were re-copied, respected, and expanded by later medical authorities for over a millennium and a half, and his name has become synonymous with the scientific and medical paradigm that prevailed from the twelfth century to the early seventeenth. Galenic medicine centers around the theory of the four humours – blood, phlegm, black bile and yellow bile: the body’s fluctuating economy of liquids that were considered necessary for health and for a balanced temperment. In this medical paradigm, the benefits of sleep included enabling the restorative transformation of food into the four humours.
Given that emotions were understood as imbalances in the humours – for instance, anger indicating a predominance of yellow bile, sorrow or melancholy a predominance of black bile – this way in which sleep acts to restore the balance between the humours makes sleep a legible response to a strong or uncomfortable emotion. Here, sleep seems to serve as a way of pressing the ‘reset button’. As Marlowe’s Dr Faustus would put it, it is a way to ‘Confound these passions with a quiet sleep’. We might refer to an angry person as in an ‘ill humour’; however, whereas today this would be a metaphorical way of speaking, in late medieval and early modern mentalities, this sort of description was firmly grounded in a literal understanding of physiology. From the holistic perspectives of Galenic medicine and of pre-Cartesian views of the interrelations between mind and body, sleep serves to return strong or unhealthy emotions – and perhaps especially emotions produced by mental stress – to equilibrium.
Premodern literary texts of a variety of genres, from Geoffrey Chaucer’s dream visions to Sir Thomas Malory’s romance of King Arthur and his Knights of the Round Table, negotiate the causal role of the emotions in engendering sleep. One early example, Chardri’s thirteenth-century version of the Life of the Seven Sleepers of Ephesus, describes how the Seven Sleepers fall asleep in the cave where they are hiding from their persecutors:
Whether out of distress or out of worry, the seven young men went to sleep – for it often happens, you know, that when people are very sad on account of the weight of their worries, it is natural that they are prompt to slumber.
This is an extraordinary sleep: a sleep from which the Seven will not awake for three centuries; a miracle demonstrating God’s power reproduced in hagiographical collections across the later Middle Ages. Chardri’s aside, however, emphasises that how or why they fall asleep is more ordinary, even expected: it is something that ‘often happens, you know’ (‘avent, sachez, suvent’). Chardri was writing at a time when knowledge of Galenic medicine had recently spread through Western Europe to England via medical tracts translated from Arabic. Chardri’s saints’ lives – in Anglo-Norman French, directed towards English audiences – speak to an understanding of sleep as a ‘natural’ or appropriate response following uncomfortable emotions such as sorrow or anxiety. Sleep is not just a reaction, it is also a renewal: by facilitating the transformation of food into the four humours, sleep could restore the balance between the humours that was necessary for good health. And as we see here, a strong imbalance in the humours was also believed to be able to generate sleep.
My forthcoming book, Sleep and its Spaces in Middle English Literature: Emotions, Ethics, Dreams, considers how, in the premodern English imagination, sleep is an embodied and culturally determined act. Sleep is both performed and interpreted by characters and contemporaries; beneficial to physical and mental health, but also bearing dangers and vulnerabilities. Premodern ideas about the dangers of sleep ranged from the supernatural noon-day demon sometimes thought to prey upon unwary sleepers, to condemnations of idleness as a sin, and to the instructions in conduct manuals and medical tracts that readers should not sleep during the day for the damage it could do to their social reputations as well as their bodily health. Yet representations of sleep are also shaped by the locus amoenus tradition, the idea of a pleasant outdoors space conducive to peaceful slumber. Sleep’s epistemological dimensions are foregrounded in the ways in which sleep enabled contemplation and enlightenment by leading to dreams and other revelations of truth and knowledge. And in addition, as the Life of the Seven Sleepers of Ephesus shows, medieval literary texts negotiate sleep’s desirable medical dimensions, viewing sleep as a natural and necessary process which required preparation and proper practice, and could ward off or alleviate disease or emotional distemper.
There was growing skepticism about Galenic humoral theory from the seventeenth century onward, when ‘Galenism as a “science” waned’. The eighteenth-century concept of sensibility (as embodied by Jane Austen’s Marianne Dashwood) gave troubled sleep a form of social or moral capital, as an inability to sleep properly became prized as a symptom of refined sentiment. Yet from the twelfth century onwards, insomnia also offered a not-entirely-dissimilar form of capital as a symptom of lovesickness, itself pathologised (as arising from a predominance of melancholy) and exploited in the portrayal of fin’ amors or courtly love, and in the genre of dream visions to which Chaucer made distinctive contributions. The seventeenth-century shift in attitudes to sleep is not one in which sleep was increasingly medicalised, but rather, one in which sleep was medicalised differently. The founding of the Royal Society in 1660 contributed to changing scientific paradigms, and during the late seventeenth and eighteenth centuries, sleep’s significance for digestion began to receive less attention than sleep’s connections to the brain and nerves, with sensibility understood as a neurological condition. The earlier interplay between sleep and the emotions was rooted in bodily processes, rather than neurological ones, but this interplay also shaped some of the strong connections between mind and body that were foregrounded in the Middle Ages – more so than after Cartesian dualism took hold in the mid-seventeenth century.
Modern sleep science, although emerging from a different medical paradigm, shares with Galenic science its view of the importance of sleep to physical and mental health, memory, dreams, and the processing of traumatic emotions. Some recent theories of the role of sleep in restoring balance to the emotions look remarkably like humoral theories on the same subject – in terms of the effects, if not the operations, ascribed to sleep. For instance, modern sleep science, like medieval sleep science, recognises that there is a complex relationship between sleep and mental health, mood and emotions, and that poor sleep increases the likelihood of depression, anxiety, and stress. At a time when psychologists are recognising that ‘mental health issues can be signalled by problems with sleep, and sleep disturbances seem to predict and lead to a range of difficulties with mental health’, we might glean something for our own time from the ways in which writers such as Chardri, Chaucer, Malory, and Marlowe attended to similar problems.
Dr Megan Leitch is Senior Lecturer in English Literature at Cardiff University. She is the author of Romancing Treason: The Literature of the Wars of the Roses (Oxford University Press, 2015), and co-editor of A New Companion to Malory (Boydell and Brewer, 2019). Her next book, Sleep and its Spaces in Middle English Literature: Emotions, Ethics, Dreams, will be published with Manchester University Press.
 Matthew Walker, Why We Sleep: The New Science of Sleep and Dreams (London: Allen Lane, 2017), p. 4.
 Jonathan Crary, 24/7: Late Capitalism and the Ends of Sleep (London: Verso, 2013); see also Alice Gregory, Nodding Off: The Science of Sleep from Cradle to Grave (London: Bloomsbury, 2018).
 Vicki Culpin, The Business of Sleep: How Sleeping Better Can Transform Your Career (London: Bloomsbury, 2018), p. ix; J. Pilcher and A. Huffcut, ‘Effects of Sleep Deprivation on Performance: A Meta-Analysis’, Sleep, 19 (1996), 318-26.
 Christopher Marlowe, Dr Faustus, ed. by David Scott Kastan (New York: Norton, 2005), A-text 4.1.135 and B-text 4.4.25.
 ‘Ke par dolur, ke par penser / Endormirent li set bacheler. / Kar ceo avent, sachez, suvent / Ke gent, quant il sunt trop dolent / Par pesance de lur penser, / Lur cuvent tost sumiller’: Chardri, La Vie des Set Dormanz, ed. by Brian S. Merrilees, ANT 35 (London: Anglo-Norman Text Society, 1977), ll. 615–20; The Works of Chardri: The Little Debate, The Life of the Seven Sleepers, and The Life of St Josaphaz, ed. and trans. by Neil Cartlidge (Tempe, AR: Arizona Centre for Medieval and Renaissance Studies, 2015), p. 50.
 This commentary on sleep as a fitting response to a strong emotion is not paralleled in Chardri’s Latin source, but is also found in Chardri’s other saint’s life, Josaphaz. ‘It sometimes happens that on account of sorrow and anxiety people find it easy to fall suddenly asleep’: Josaphaz, ll. 1943–44; Cartlidge, The Works of Chardri, pp. 101-02.
 Charles Burnett, The Introduction of Arabic Learning into England (London: British Library, 1997), p. 28; see also Shazia Jagot, ‘Fin’ amors, Arabic Learning, and the Islamic World in the Work of Geoffrey Chaucer’ (unpublished doctoral thesis, University of Leicester, 2013), esp. p. 34.
 Stephen Pender, ‘Subventing Disease: Anger, Passions, and the Non-Naturals’, in Rhetorics of Bodily Disease and Health in Medieval and Early Modern England, ed. by Jennifer C. Vaught (Farnham: Ashgate, 2010), pp. 193-218 (p. 195).
 Sasha Handley, Sleep in Early Modern England (London: Yale University Press, 2016), pp. 181-82.
 On the medicalisation of sleep from the thirteenth through sixteenth centuries, see Pedro Gil Sotres, ‘The Regimens of Health’, in Western Medical Thought from Antiquity to the Middle Ages, ed. by Mirko D. Grmek (Cambridge, MA: Harvard University Press, 1998), pp. 291-318; Nancy G. Siraisi, Medieval and Early Renaissance Medicine: An Introduction to Knowledge and Practice (Chicago, 1990), esp. p. 101; William F. MacLehose, ‘Fear, Fantasy and Sleep in Medieval Medicine’, in Emotions and Health, 1200-1700, ed. by Elena Carrera (Leiden: Brill, 2013), pp. 67-94; and Karl H. Dannenfeldt, ‘Sleep: Theory and Practice in the Late Renaissance’, Journal of the History of Medicine and Allied Sciences, 41 (1986), 415-41.
 Handley, Sleep in Early Modern England.
 Walker, Why We Sleep; Gregory, Nodding Off.
 Matthew Walker and E. van der Helm, ‘Overnight Therapy? The Role of Sleep in Emotional Brain Processing’, Psychological Bulletin, 135 (2009), 731-48.
 See, for instance, A. Steptoe, K. O’Donnell, M. Marmot and J. Wardle, ‘Positive Affect, Psychological Well-Being and Good Sleep’, Journal of Psychosomatic Research, 64 (2008), 409-15; D. Tempesta, A. Couyoumdjian, G. Curcio, F. Moroni, C. Marzano, L. De Gennaro, and M. Ferrara, ‘Lack of Sleep Affects the Evaluation of Emotional Stimuli’, Brain Research Bulletin, 82 (2010), 194-208; Culpin, The Business of Sleep, pp. 69-77.
 K. Barnett and N. Cooper, ‘The Effects of a Poor Night’s Sleep on Mood, Cognitive, Autonomic and Electrophysiological Measures’, Journal of Integrative Neuroscience, 7 (2008), 405-20.
 Gregory, Nodding Off, p. 150; see also P. K. Alvaro, R. M Roberts, and J. K. Harris, ‘A Systematic Review Assessing Bidirectionality between Sleep Disturbances, Anxiety, and Depression’, Sleep, 36 (2013), 1059-68, and D. Freeman, B. Sheaves, G. M. Goodwin et al., ‘The Effects of Improving Sleep on Mental Health (OASIS): A Randomised Controlled Trial with Mediation Analysis’, Lancet Psychiatry, 4 (2017), 749-58.