Patients will be assigned to a chamber with or without bright light therapy. This assignment is based on occupation of ICU beds and availability of nurses and is therefore independent from patients characteristics. All patients of 18 years and older who will be admitted to the Intensive Care Unit of the Onze Lieve Vrouwe Gasthuis, Amsterdam can be included in the study. Patients diagnosed with bipolar disorder will be excluded from participation. Other exclusion criteria are the use of an antipsychotic drug in the home environment, temporary or permanent loss of total vision and participation in this study during a previous admission to the Intensive Care Unit.