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. Patients will be included following the inclusion criterion and exclusion criteria. Patients assigned to a chamber with bright light therapy will receive light therapy for three hours in the morning, from eight o'clock till eleven o'clock. The Confusion Assessment Method-score (CAM-score) and the Richmond Agitation Sedation Scale-score (RASS-score) will be performed three times at one day by ICU nurses, this is according to the existing routine. Besides this, an extra CAM-score and a clinical assessment will be performed once a day by a trained non-clinician, to determine the presence of delirium. The use of sedatives, haldol and fixation will be registered to determine the occurrence, duration and severity of delirium. Eventually the most important outcomes will be the clinical assessment of the patients, the CAM-score and the use of haldol. The primary outcome of this study is the duration of delirium, defined in number of days.