When the sun only appears briefly in winter, we often feel exhausted. Some people become more susceptible to depressive illnesses due to the lack of light. So-called light therapy is supposed to help people who are prone to winter depression. How does winter depression occur? And how effective is light therapy?
Driving to work in the dark and driving back in the dark – the short autumn and winter days are stressful for many people. They complain about a bad mood, lack of motivation or a lack of energy. If this low mood becomes severe, doctors speak of winter depression.
A disease of modern society?
In winter depression, in addition to the usual symptoms of depression, variants of these symptoms also occur: For example, those affected then have increased cravings, especially for foods rich in carbohydrates, instead of suffering from the loss of appetite that is more typical of seasonal depression. Those affected by winter depression also tend to have a stronger need for sleep rather than difficulty falling asleep and staying asleep.
Some researchers interpret this reaction as an evolutionarily sensible adaptation to the dark season. Less activity, more sleep and increased energy intake may have previously helped people survive the winter with scarce resources. Only in modern society, in which artificial light, food and performance requirements are constant all year round, does this biological rhythm increasingly come into conflict with everyday life.
The internal clock gets out of sync
The exact causes of winter depression have not yet been fully clarified, but the lack of sunlight is considered a central influencing factor. It controls our biological daily rhythm and acts as an important clock for our internal clock. When light hits the retina, special visual cells send signals to the brain that prepare the body for alertness and activity. Under these light signals, increased amounts of serotonin are released in the brain – a messenger substance that stabilizes mood. At the same time, light inhibits the production of the sleep hormone melatonin.
In winter, this balance shifts: the long periods of darkness lead to lower serotonin and higher melatonin levels. In addition, there is reduced production of vitamin D due to the lack of sunlight. For some people, this can disrupt their internal clock and trigger seasonal depression.
Those affected by ADHD are particularly susceptible: their risk of developing winter depression is increased tenfold. Just over a quarter of people with ADHD also have seasonal depression, according to a study. Researchers suspect that both their light processing and the control of their internal clock react more sensitively to a lack of light and that vitamin D deficiencies also occur more frequently.
How effective is light therapy?
Light therapy is often recommended for those affected by winter depression. They should expose themselves to a strong light source for 30 to 40 minutes every morning and consciously look into the light from time to time. A lamp with an illuminance of 10,000 lux is ideal. For comparison: lighting in living rooms has around 100 to 300 lux, an overcast winter sky has 6000 lux and an overcast summer day has 20,000 lux. But does that really help?
The Institute for Quality and Efficiency in Healthcare (IQWiG) evaluated 21 studies dealing with light therapy. Accordingly, light therapy can reduce depressive symptoms in the short term somewhat more than placebo treatment. “With therapy, for example, after two to eight weeks, the symptoms of 46 out of 100 people had improved significantly,” explains IQWiG. “Without therapy, this was the case for 25 out of 100 affected people. That means: around 21 out of 100 people benefited from the use of the light lamps.”
Other studies compared this form of therapy with taking the antidepressant fluoxetine or cognitive behavioral therapy: “With all three treatment methods, the symptoms had improved to a similar extent after five to eight weeks: in around half of the people, the depression had disappeared,” the institute continued.
What should you consider when buying a lamp?
If you suffer from winter depression, you should, if possible, consult your doctor to see whether light therapy is a suitable treatment method for you. Under certain conditions, statutory health insurance companies cover part of the costs for light therapy. However, winter depression must first have been diagnosed by a doctor.
When used correctly, a “light shower” with a daylight lamp is not harmful and can also help those who are not affected feel better in the dark season. There are some over-the-counter lamp models available in stores: Buyers should make sure that the illuminance is sufficient and that the luminous area of the lamp is sufficiently large. Good devices are also available for little money.