Sun lamps really help SAD

Light therapy for depression

It has long been known that sunny days and a bright, light-flooded environment have a positive effect on the mind. Today the antidepressant effects of light are used to treat seasonal depression.

When the days get shorter and the temperatures slowly drop again outside, many people find it difficult to get out of bed, they feel drained and dull during the day. If the sunlight slowly decreases in autumn, many people experience the first signs of seasonal affective disorder (SAD) - better known as autumn-winter depression. However, light therapy can help prevent seasonal depression and alleviate symptoms during the dark months.

How does light affect the body?

Today we know: light influences the circadian rhythm - our internal clock. This is responsible for important body functions: when we are hungry, which hormones are produced and how we feel.

The light is picked up by the retina of the eye and converted into electrical impulses that reach a brain structure - the nucleus suprachiasmaticus. This guides the rhythm of light or brightness and darkness - the so-called sleep-wake rhythm - to certain parts of our brain that are responsible for different functions of our body. These functions include the release of the sleep hormone melatonin, which is suppressed when there is light and produced when it is dark. The sleep hormone is attributed, among other things, to a depression-promoting effect. Blood pressure, body temperature, feeling of hunger, sexual need and our mood are also regulated by the daily rhythm of light and darkness.

What is Seasonal Depression (SAD)?

Some people react more to changes in light and some less. In our latitudes around one in five is affected by a seasonally dependent depression in the dark autumn and winter months (mostly year after year). This means a significant deterioration in well-being with the following symptoms, among others:

  • depressed mood
  • Listlessness
  • Increased appetite
  • Daytime sleepiness
  • Neglect of social contacts
  • Increased need for sleep
  • Difficulty concentrating

+++ More on the topic: Winter Depression +++

How does light therapy work?

Light therapy is mainly used to treat seasonal depression. The lack of daylight in the autumn and winter months is replaced by special light therapy lamps. Light therapy must be distinguished from phototherapy, which is used to treat skin diseases such as neurodermatitis, psoriasis (psoriasis) and other eczema. With light therapy, the person concerned sits relaxed at home in front of the light apparatus (also called daylight lamp or light shower), which consists of six to eight fluorescent tubes. These tubes emit a bright white fluorescent light that - apart from the ultraviolet component - contains the entire spectrum of the light. The light intensity on the eye is between 2,500 and 10,000 lux, depending on the device used and the distance from the lamp. This corresponds roughly to the light on a bright, beautiful spring day.

The antidepressant effect of the daylight lamp is conveyed via the eye, as with natural light. Here, too, the retina converts the light signals into nerve impulses. This influences certain brain structures that are responsible for the sleep-wake rhythm and other daily rhythms of humans.

The exact mechanism is not yet known. Since melatonin is associated with a depression-inducing effect, it is assumed that light therapy stops the production of the sleep hormone immediately after waking up in the morning and this leads to a positive change in mood. The period of the day or the light time of the day is thus extended, which has a positive effect on the well-being. Another explanation assumes that light therapy increases the concentration of messenger substances in the brain, including the concentration of the transmitter substance serotonin, which is closely related to the development of depression. Recently, more and more data support the suggestion that treatment with light is effective in all forms of depression.

How is light therapy used?

The light therapy should best be carried out daily, depending on the type of device, for 30 to 60 minutes at a distance of around 60 to 70 cm from the lamp. During the application you can write, eat, make phone calls or do some other activity. Just make sure to keep the correct distance and look directly into the light source for a few seconds once a minute. It should be noted that closing your eyes or wearing sunglasses during treatment does not make sense. Because the light signals cannot be passed through the eyes to the brain.

The daily recommended duration of light therapy varies from half an hour to four hours. According to studies, the time of day is not decisive. At the beginning of the treatment, it is recommended to sit in front of the device at fixed times in the morning and / or in the evening. However, since in some cases it can lead to problems falling asleep in the evening, it is recommended to carry out light therapy at the beginning of the day. In patients with seasonally dependent depression, the antidepressant effect usually becomes apparent after three to four days.
Depending on the device, you start with 2,500 lux for two hours a day or 10,000 lux for half an hour. If this treatment does not show a clear antidepressant effect, the daily treatment duration should be increased to four hours. Patients with severe depressive moods should consider other therapeutic measures in addition to light therapy. Those who do not respond at all to light therapy should be treated with antidepressants or other procedures.

What side effects can light therapy cause?

Light therapy is easy to use, has little stress and does not cause any serious side effects. Very rarely, if ever, do users complain of headaches, burning, irritated eyes or dry skin. Such complaints usually go away after a short time. Irritation and manic moods are also very rare (euphoria, increased drive, increased flow of speech). If the light therapy is carried out in the evening, it may therefore lead to problems falling asleep. The side effects usually only occur in the first few days of treatment. In this case, you should first reduce the daily duration and intensity of light therapy and only increase it again when the treatment is tolerated. If those affected receive tricyclic antidepressants or lithium in addition to light therapy, an ophthalmologist should monitor the course of treatment in order to detect any damage to the retina at an early stage. In general, a previous ophthalmological examination is recommended, because caution is required with certain eye diseases. Since the effect of light therapy only lasts for a very short time - about one to two days - it is also necessary to carry out the treatment, preferably daily, in order to achieve the desired effect.

Which additional measures or alternatives can be used to light therapy?

Since natural light - even when the sky is overcast - is at least as effective as the artificial light from a daylight lamp, you should spend as much time outdoors as possible (e.g. cycling, cross-country skiing, walking, etc.) - preferably in the morning hours. Well-structured daily planning can also help to combat the gray monotony in the darker months of the year.

Some depressed people respond little or not at all to treatment with light and should therefore be treated with another form of antidepressant treatment. This includes, among other things, drug treatment with antidepressants. Psychotherapy can also be effective in treating seasonal depression.

+++ More on the topic: Psychotherapy for depression +++

Who do I contact when I first see signs of seasonal depression?

Those affected should first clarify their concerns and complaints with their family doctor. If necessary, he or she can issue a referral to a specialist in psychiatry. The treating psychiatrist then decides on the further course of treatment. The AKH in Vienna also has its own outpatient clinic for the treatment of autumn-winter depression. If a light therapy is prescribed, light lamps can also be tested there.

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Dr. Matthias Thalhammer (first author, 2004), Tanja Unterberger (2016)
Medical review:
O. Univ. Prof. Dr.h.c. mult. Dr med Siegfried Kasper
Editorial editing:
Katrin Derler, BA

Status of medical information:

Kasper & Rosenthal: Light therapy - the program against autumn and winter depression, Kneipp-Verlag, 1st edition, Vienna, 2010

Sekharan et al .: The Active Site of Melanopsin: The Biological Clock Photoreceptor. In: J. Am. Chem. Soc., Volume 134, 2012, pp. 19536–19539 (Online, last accessed: October 24, 2016)

ICD-10: F32.0, F32.1, F32.2, F32.3, F32.8, F32.9