Chasing the Sun: The New Science of Sunlight and How It Shapes Our Bodies and Minds (Wellcome Collection) by Linda Geddes

Author:Linda Geddes [Geddes, Linda]
Language: eng
Format: epub
Goodreads: 42603316
Publisher: Wellcome Collection
Published: 2019-01-10T00:00:00+00:00

6

A Dark Place

AS EARLY AS the second century AD, the celebrated ancient Greek physician Aretaeus of Cappadocia commanded that, ‘lethargics are to be laid in the light, and exposed to the rays of the sun (for the disease is gloom)’.1 The Yellow Emperor’s Classic of Medicine, a Chinese medical tome estimated to have been written around 300 BC, also describes how the seasons induce changes in all living things, and suggests that during winter – a time of conservation and storage – one should ‘retire early and get up with the sunrise … Desires and mental activity should be kept quiet and subdued, as if keeping a happy secret.’2 And in his Treatise on Insanity, published in 1806, the French physician Philippe Pinel noted a mental deterioration in some of his psychiatric patients ‘when the cold weather of December and January set in’.3

No more strongly is this felt than at the high latitudes of Scandinavia, where, during winter, daylight dwindles to a mere few hours per day – or vanishes completely. In the northern part of Sweden, winter depression is known as lappsjuka, or ‘the sickness of the Lapps’. Even the sixth-century historian Jordanes noted the seasonal peaks of cheer and sorrow among the Adogit people who inhabited Scandinavia at that time. ‘To have continual light in midsummer for forty days and nights, and likewise no clear light in the winter season … They are like no other race in their sufferings and blessings,’ he wrote.4

For the minority of people who suffer from seasonal affective disorder (SAD), and for the very many of us who suffer to some degree from winter blues, winter is literally depressing.5

The modern story of SAD as a syndrome dates to the late seventies, when a team of researchers at the National Institute of Mental Health (NIMH) in Maryland, who had been investigating how light affects biological rhythms, were approached by Herb Kern, a short, sixty-three-year-old engineer with a crew cut.

Brimming with energy and enthusiasm, Kern had been keeping detailed records of his bipolar mood swings since 1967, and was convinced that they showed a seasonal pattern, which related to the length and intensity of sunlight. To try to validate his theory, Kern had joined the American Society of Photobiology and had already spoken with several researchers in the field about his mood swings.6

Two NIMH investigators, Alfred Lewy and Sanford Markey, had recently published a report on a new method of measuring melatonin levels in human blood plasma: Kern wanted them to test his blood during spring and winter, to see if they could identify biological differences that might account for his changing moods.7

Lewy and his colleagues already knew that day length dictated seasonal changes in the biology of certain animals, and that it was the duration of melatonin secretion (that biological beacon of the night) that told their bodies what time of year it was. They had also just demonstrated that melatonin secretion could be suppressed in humans if they were exposed to bright light.

The

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