Light influences humans not only visually, but also by controlling the internal clock and overall well-being. It affects the brain by inhibiting the production of the sleep-promoting hormone melatonin and stimulating the release of the mood-enhancing hormone serotonin, which has a positive effect on mood. Daylight is particularly important here, as it lifts the mood, supports vitamin D metabolism, and promotes performance and concentration.

Daylight can be simulated by technical devices such as daylight simulators or through the use of specific lighting like LED windows. In private environments, smart lights can also be used to mimic a sunrise, or the effects of sunlight can be replicated using daylight lamps. When someone switches on a daylight lamp or a light box in the morning, bright, UV-filtered light is transported through the retina into the nerve pathways that govern the internal clock: the day-night rhythm stabilizes, the sleep hormone melatonin drops at the appropriate time, and motivation increases. At the same time, systems linked to mood and motivation are activated. This biological mechanism explains why people feel more awake and better after using a daylight lamp.

For seasonal depression, also known as winter depression, light therapy is recognized as an established, scientifically proven treatment.

For all other forms of depression, light can be particularly helpful as a supplementary measure. Individuals already undergoing psychotherapy can achieve additional relief from their depression through light therapy. This is especially true if the person's sleep-wake cycle has shifted significantly and they are suffering from a severe lack of drive.

Light therapy for depression is not a substitute for comprehensive treatment. Experts recommend a combination of Cognitive Behavioral Therapy (CBT), providing education about the illness (psychoeducation), and active daily self-management by the individual. If needed, medication in the form of antidepressants can also be taken. Light therapy can enhance the effectiveness of this combination.

deprexis is a Digital Health Application (DiGA) that supports people with depression in their daily lives with knowledge, inspiration, and concrete exercises. With the support of deprexis, individuals can independently apply strategies to manage their symptoms and strengthen their mental health. This includes structuring the day, integrating physical exercise and pleasant activities, tracking one's mood, and learning relaxation techniques. deprexis can be prescribed by a primary care physician, and the costs are typically covered by health insurance.

The greatest factor in the success of light therapy is consistency: do your light therapy every day in the morning, ideally within the first hour after waking up. Position yourself in front of the lamp so that the light reaches your eyes, but do not look directly into the light source—instead, look slightly to the side of it. You can read, have breakfast, or check emails during the session. The only important thing is that your eyes remain open.

1. Use a daylight lamp with 10,000 lux.
2. Ensure you use a device with a UV filter to protect your eyes and skin.
3. Make sure the lamp is flicker-free – flickering can promote headaches.
4. Maintain a distance of 20–50 cm; a greater distance reduces the effectiveness.
5. Keep your eyes open for 20–30 minutes and look slightly past the light, not directly into the lamp.
6. If you use a weaker lamp (e.g., 5,000 lux), the required duration of use increases.
7. Integrate the use of the daylight lamp into your daily routine: for example, place the light box at your breakfast table.
8. Avoid sessions after 4 p.m. Bright light late in the day can disrupt your sleep-wake cycle.
9. Keep taking every opportunity to get natural daylight anyway. The combination enhances the overall effect.
10. If you are unsure: ask your primary care physician for guidance.

When used correctly, light therapy for depression is considered a safe and well-tolerated method. Nevertheless, the following side effects can occur, albeit rarely:

• Headaches – especially if users look directly into the lamp after all.
• Eye irritation – for the same reason.
• Nervousness or mild restlessness.
• Mild sleep disturbances – if the daylight lamp is used after 4 p.m., contrary to recommendations.

If you want to avoid these rare side effects, make sure to only use the light during the morning, increase your distance from the lamp, or shorten the duration of the session.

In certain cases, a medical assessment is absolutely necessary before starting light therapy with a daylight lamp:

Bipolar Disorder

• Explanation: Light that is too intense or used too late in the day can trigger a shift into overactivity (hypomania or mania). Therefore, a medically supervised, often shorter, and very early-morning application—or an alternative treatment—is required.

Eye Diseases

• Explanation: Certain conditions, such as those affecting the macula (the "yellow spot" at the center of the retina), or recent eye surgeries, make a consultation with the treating physician or ophthalmologist necessary.

Photosensitizing Medications

• Explanation: Taking medications that can make the skin sensitive to light, such as certain antibiotics, neuroleptics, or even St. John's wort, can cause your skin to become hypersensitive to light.

The market for daylight lamps is vast. However, not every lamp is automatically a therapeutic lamp.

Good light boxes usually cost between 100 and 250 euros. For home use, light therapy is not a standard benefit covered by public health insurance funds. Therefore, the following applies:

• Self-payer: In most cases, you have to bear the costs yourself.
• Case-by-case decisions: Some insurance companies review individual cases. Especially in the case of severe seasonal depression and a specialist's recommendation, it can be worthwhile to inquire with your insurance provider.
• Alternatives: Some providers offer rental devices. Devices are also available for use in inpatient settings or in certain specialist medical practices.