As with sleep, other environmental factors have frequently been cited as being causes of ICU syndrome without due scrutiny of the empirical basis for this conclusion. Social isolation, immobilization, unfamiliar surroundings, excessive noise, and sensory monotony or absence of diurnal light variation have all been implicated. The ICU environment is replete with stress-inducing levels of noise, lighting, and movement. Several studies have documented that decibel levels in ICUs exceed the recommended normal levels.31,32 While these factors may place a degree of stress on a person, they are not documented causes of altered consciousness, delusions, or perceptual disturbances of the quality or severity seen in delirium,33 nor are these factors necessary conditions for delirium to occur. With sufficient organic problems, a person will develop delirium regardless of the environment.