Electric indoor lighting can disturb sleep and increase depressive symptoms; both common complaints in psychiatric inpatients.

To improve quality of sleep in patients using an indoor hospital lighting environment simulating nature in intensity, color, and circadian timing.

Investigator-blinded parallel group randomized controlled effectiveness trial supplied with qualitative interviews in an inpatient psychiatric ward with fully automatic and adjustable lighting. Admitted patients received a room with a naturalistic lighting environment (intervention group) or lighting as usual (control group). The primary outcome was the Pittsburg Sleep Quality Index and secondary outcomes included the Major Depression Inventory and WHO-five Well- Being Index.

In this ongoing trial, we included 28 patients (16 treated and 12 controls). Patients in the intervention group reported higher subjective sleep quality and sleep efficiency, lower use of sleep medication (mean difference, 4.68 mg; 95% CI, 0.54; 53.5), fewer depressive symptoms (mean difference, 5; 95% CI,–2; 13), but lower well-being (difference,–4 percentage points; 95% CI,–20; 16), compared with the control group. At discharge, fewer patients in the intervention group had experienced use of involuntary treatment. Qualitative data indicated no side effects apart from issues in performing indoor leisure activities in dim light.

A naturalistic lighting environment was safe and improved sleep and mood in our small patient sample. The trial integrated well with routine clinical care and our sample reflected the heterogeneity of the target population (Funded by Region Midtjylland and others; Clinicaltrials.gov number, NCT02653040)

The authors have not supplied their declaration of competing interest.