Human beings have been on earth since the Stone Age (around 100,000 years ago), and it is only in the last 200 years, following the Industrial Revolution, that billions of people have moved into cities. Way back, we lived in roving, close-knit bands following a hunter-gatherer way of life. We lived in places like the savannahs of Africa where it is hot and there are serious levels of sunlight.

Light pic

Modern survival often means living in cold, dark places and working long hours inside. Simultaneously, rates of sleep and mood disorders are growing. Could the lack of light have something to do with it? Rates of depression and sleep disorders are far higher in developed countries than among rural folk. Northern European countries (with long winters and long nights) have much higher rates of depression, suicide, and alcohol abuse. Could it be the lack of light has some effect?

Light is measured in lux – the amount of light which hits the surface area of your retina at one time. One lux is about the level of light on a full moon. On a grey day, light hits your retina about 10,000 times more. This is called 10,000 lux. And on a hot, sunny, summer day about lunchtime, there can be about 100,000 lux that reach the retina. Hunter-gatherers spent the day outside, exposed to sunlight at very high rates. No sunglasses, no umbrellas, no office buildings, no cars. In a typical rest-home in Western society, for instance, people are exposed to about 50-200 lux reach the retina. That’s a phenomenal difference.

Light is important for mood and sleep. Light exposure triggers the circadian rhythm which controls sleep. Back in the day, when it was getting dark, we went to sleep. When the sun came up, we got up. Today, we have artificial means of making it stay light and many other ways in which we are exposed to light (use of laptops, mobile phones, television). This artificial stretching out of the day means our sleep hormone (melatonin) is not being triggered to release in the same way. Our bodies are confused about when to sleep, and many of us have lost our ‘circadian’ rhythm. This can result in a range of sleep problems. And sleep problems are associated with many other difficulties such as anxiety, depression, stress, burnout, etc.

If you, or anybody you know, has difficulty with sleep, contact us to talk to one of our psychologists who can put you on the right track and begin to “shed some light” on your problem.

As Sophocles once said, “Sleep is the only medicine that gives us ease.”