Causes

To understand the origin of such a disorder, it is necessary to explain some basics: Every human being is subject to a so-called day-night rhythm (circadian rhythm), which, put simply, ensures that we sleep when it is night and that we are awake when the sun is shining. For this rhythm to work at all, regular timers (such as sunlight) are needed. If a person is denied such timers, the day-night rhythm gets confused.

This can be observed, for example, in prisoners who live in constant darkness day and night. Excessive night and disco life can also lead to a change in the day-night rhythm. In winter, when the nights become longer and the days shorter, the stimuli for “adjusting” the day-night rhythm change.

It is assumed that this (among other changes) can lead to a depressive mood. Today, a reduction of the so-called “serotonin” is held responsible for this development. Serotonin, often called the “happiness hormone” in the vernacular, is a so-called “neurotransmitter“, i.e. a messenger substance that mediates information between nerve cells.Nowadays it is assumed that serotonin in particular is responsible for a balanced mood.

Serotonin is typically released into the blood during the day. However, it needs a stimulus beforehand to switch the brain to “daytime activity”. These signals are reduced in winter by a changed and shortened light incidence into the eye.

Directly related to serotonin, the so-called “melatonin“, also known as “sleep hormone”, must be mentioned here. This melatonin naturally ensures that the body can enter a deep sleep phase at night. A direct incidence of light into the eye (light timer) now ensures that in the morning the melatonin production is stopped and the (above mentioned) serotonin production and release into the blood is increased.

In winter in our latitudes there are fewer stimuli that stop the melanin production due to the long nights. This results in increased melatonin and decreased serotonin levels. It is now known that a permanently too low serotonin level (or increased melatonin level) increases the probability of developing depressive symptoms.

For most people, daylight has an important influence on mood. For some this influence is so essential that they can develop depression if there is a lack of daylight. The connection between depression or winter depression in particular and vitamin D deficiency has been and is the subject of numerous studies.

Vitamin D is only produced sufficiently by the body if it has enough daylight available. If this is not the case, a vitamin D deficiency can occur. This leads to symptoms such as increased bone fragility and bone pain.

The common denominator of winter depression and vitamin D deficiency therefore appears to be a lack of daylight. Some studies have shown that a lack of vitamin D, which in turn is caused by a lack of light in the winter months, could be a causal factor in the development of winter depression. In several studies a too low vitamin D level was found in patients with depression.

Also the effect of a light therapy was compared in a study with that of the Vitamin D substitution with depressive patients. In these studies the administration of Vitamin D had a stronger effect. Other studies could not establish a safe connection between Vitamin D and depression.

Accordingly there are so far no recommendations for regular vitamin D substitution in depressive patients. It is possible to determine the vitamin D level in patients suffering from winter depression. If the level is too low, a substitution therapy with vitamin D can be started.

However, it should be mentioned that in healthy people who regularly go out into the fresh air a vitamin D deficiency is rare. It is much more common in older people (or young people who spend most of their days sitting at the computer) who are tied to the house or apartment and hardly ever go outside. Also people who permanently work at night and sleep during the day can have an increased risk of a vitamin D deficiency.