Depression is a major health challenge, and despite developments in pharmacotherapy and psychotherapy a substantial part of patients will only recover very slowly and incompletely, and 10-25 % of the patients are resistant to treatment. Therefore, new treatment initiatives are in demand. Chronotherapeutics can regulate diurnal rhythms and sleep, and have shown promising results on antidepressant effects. Among chronotherapeutic treatment modalities, Bright Light Therapy (BLT) has been used in treatment of depression and sleep disorders for several decades with both an antidepressant and a sleep improving effect. BLT has also been shown to augment antidepressant therapy.

Objectives. The objective of this trial is to investigate the feasibility of a combination of LED-light armatures aiming to mimic sunlight, when installed in the patient rooms of a psychiatric inpatient Ward. Investigators has opted for using a randomized design that will subsequently be tested in a larger clinical trial with depression severity as the primary outcome. In this feasibility study investigators will register the stability of the system, the influence of the light on patients regarding tolerability, comfort, depression level, and sleep. Investigators also so want to measure and collect specific light-data on the Non-image-forming light (NIF) by using specially designed light sensors to capture the spectral distribution of the light. Finally investigators will test the electronic case report form (eCRF) that has been designed for the trial.

Design. The design is a randomised controlled feasibility trial with two arms: an active dynamic light trial arm and a standard light trial arm with blinding of depression outcome assessors (Hamilton depression rating scale), data collection, and data analyses. Randomization will be with a rate for active and standard of 2 to 1.

Inclusion and exclusion criteria. Inclusion: Major depression disorder, age > 18 years, informed consent and Danish speaking.

Exclusion: Severe suicidality, actual psychotic state, bipolar disorder and if the patient is subject to coercive measures of any kind.

Name and description of experimental and control intervention. The experimental intervention is the implementation of a dynamic LED-light system in two patient rooms. The system includes three elements: a window jamb built-in light panel, two ceiling mounted lamps, and a wall mounted lamp. All lamps will have a dynamic, time dependent frequency distribution and intensity of light. The control intervention is constant standard LED-light with two elements: two ceiling mounted lamps and a wall mounted lamp.

Primary and secondary outcomes.

Primary outcome:

1. Rate of patients discontinuing the trial due to discomfort from the lighting condition.

Secondary outcomes:

1. Mean scores on the visual comfort scale in the intervention period
2. Reduction in HAM-D17 scores from baseline to week 4 Trial size. In total 15 patients. All regulatory approvals has been met from the Danish Data Protection Agency, the regional Ethics Committee Agency, and the Mental Health Services of Copenhagen.

Time schedule. The first participant is expected to be enrolled in December 2017. The expected last follow-up of the last participant will be June 2018. Data will be analysed from June 2018 till December 2018. Manuscripts will be prepared from June 2017 and we expect to submit first manuscript January 2019.

Inclusion Criteria:

• Major depression disorder
• Age > 18 years
• Informed consent and Danish speaking.

Exclusion Criteria:

• Severe suicidality
• Actual psychotic state
• Bipolar disorder
• Patient is subject to coercive measures of any kind.

Hamilton depression interview is done by external assessor blinded to condition