The trial takes place in 4 psychiatric closed wards at Ny Psykiatri Bispebjerg. The objective is to compare, retrospectively, over two consecutive winter periods (2022 and 2023) the effect of the lighting on the duration of stay of the patients. During the first winter, a standard lighting is used, and, during the second winter, the lighting will be modified to favor a greater light intensity in blue wave color light in the morning and a gradual decrease in light intensity in the evening adjusted for geographical orientation of the patients' rooms.

Light has benefits in many pathologies, especially in psychiatry and sleep disorders. It is the most powerful Zeitgeber, allowing a drive of the sleep-wake rhythm. But what are the "doses or quantities" of light necessary for humans to stimulate circadian regulation? And how is it possible to promote better people's exposure to this amount of light during winter (especially in Nordic countries where daily light exposure during winter is particularly reduced: 8 hours on average)? At the Bispebjerg Hospital, following the installation of LED lighting, a dynamic system favoring a greater light intensity in blue wave color light in the morning and a gradual decrease in light intensity in the evening adjusted for geographical orientation of the patients' rooms is evaluated. This device was effective on anxious and depressive symptoms for patients hospitalized after a stroke. Here, we'll study the effect the light may have on patients in psychiatric closed wards. Moreover, we'll assess the users' satisfaction and the energy consumption of the system.

If the described intervention is associated with a reduction in the duration of stay of the patients in the ward as well as with a general satisfaction of the users and that it consumes much less energy, one could think of the installation of this system on a large scale not only in hospitals but also in schools or other public buildings where it could be interesting to have this adapted lighting.

Inclusion Criteria:

• patients being 18 years old or older
• patients having a duration of stay of at least 3 days in the wards

Exclusion Criteria:

• patients that have switched room during their stay
• patients that have been in rooms where the lighting wasn't working

Patients above 18 years old that have been hospitalized in one of the 4 closed wards of NPB during the 2 study periods.