BACKGROUND: Patients admitted for rehabilitation often lack sufficient natural light to entrain their circadian rhythm.

OBJECTIVE: Installed diurnal naturalistic light may positively influence the outcome of depressive mood, anxiety, and cognition in such patients.

METHODS: A quasi-randomized controlled trial. Ninety stroke patients in need of rehabilitation were randomized between May 1, 2014, and June 1, 2015 to either a rehabilitation unit equipped entirely with always on naturalistic lighting (IU), or to a rehabilitation unit with standard indoor lighting (CU).Examinations were performed at inclusion and discharge. The following changes were investigated: depressive mood based on the Hamilton Depression scale (HAM-D6) and Major Depression Inventory scale (MDI), anxiety based on the Hospital Anxiety and Depression Scale (HADS), cognition based on the Montreal Cognitive Assessment (MoCA) and well-being based on the Well-being Index (WHO-5).

RESULTS: Depressive mood (MDI p = 0.0005, HAM-D6 p = 0.011) and anxiety (HADS anxiety p = 0.045) was reduced, and well-being (WHO-5 p = 0.046) was increased, in the IU at discharge compared to the CU. No difference was found in cognition (MoCA p = 0.969).

CONCLUSIONS: This study is the first to demonstrate that exposure to naturalistic light during admission may significantly improve mental health in rehabilitation patients. Further studies are needed to confirm these findings.