Light & Health, Light and Life

Light therapy – not just a topic for the winter

Winter is the proverbial dark season: the days are short and the sun no longer has the power to prevail against fog and clouds. More and more people suffer from light deficiency depression during this time, also known as winter depression, and medically referred to as seasonal affected disorder (SAD). The number of people affected with mild symptoms is estimated to be around 20%. Pronounced symptoms are found in around 2 – 5% of people, mainly over the age of 20 and with a significantly higher proportion of women.

The cause of this seasonal depression is primarily lack of light. In Northern Russia, Scandinavia and Canada, this health problem, which is much more prominent there, has always been known, but it is becoming increasing noticeably in our latitudes, perhaps also due to the overlap with ever more severe psychosocial problems in the modern environment. At our workplace or in our apartments, we regularly find ourselves in light levels of 300 – 600 lux, rarely more. A gloomy winter’s day, on the other hand, brings it to 3,000 lux, a beautiful one even to more than 10,000 lux. But if we do without the bright light during the day and then turn night into day with artificial light (science calls it “biological darkness”), our inner clock is out of rhythm – an indispensable “clock generator” that controls our day-night rhythm via neurotransmitters and hormones as well as having a huge influence on our well-being.

What we often miss completely in winter is venturing outside, where the brightness levels, even in bad weather, still exceed those indoors many times over. A walk of at least half an hour a day or regular exercise in nature is therefore the best “remedy”.

But, with (artifical) light therapy, the circadian rhythm, our inner clock, can also be brought back into balance. However, this requires ten times the normal lighting values and the observance of some rules:


1. From about 6,500 lux, the photoreceptors (ganglion cells) in the eye react to the incidence of light: 10,000 lux is ideal.

2. The light should have as high a blue component as possible (cold white >5,000° Kelvin) and fall from above at an angle (as with zenith light, e.g. 0 – 50°).

3. From 6,500 lux you should expose yourself to the light for between 30 minutes to an hour, from 10,000 lux a session of 15 – 30 minutes is usually sufficient, and depending on your needs either daily or one to three times a week.

4. Light therapy should be performed in the morning, preferably by 8 or 9, but no later than 12 noon, because it lowers, according to the morning light in nature, the production of the sleep hormone melatonin and stimulates the production of cortisol, which triggers the metabolism and programs us to work during the day.

Light therapy helps, especially in the dark season, to reset the internal clock, which leads to a balanced day-night rhythm and also positively influences the production of the “feel-good hormone” serotonin. Towards the evening, you should not expose yourself to bright light intensities so as not to risk melatonin production, which starts after about 6 pm, and therefore achieve healthy sleep.


Heinrich Remagen
Managing Director Remagen – Ideen für Licht + Raum e.K.
Lighting Expert

(Photo credit: © fotolia, Eray)