The Delirium and Catatonia (DeCat) Prospective Cohort Investigation is a study of critically ill patients at Vanderbilt University Medical Center, nested within our groups ongoing studies. The overarching goal of DeCat is to understand the prevalence, risk factors for and resulting morbidity and mortality from forms of acute brain dysfunction (delirium and catatonia) in the context of critical illness. Once we are able to understand more about the epidemiology of the co-occurrence of delirium and catatonia in the context of medical illness, we hope to be able to move toward understanding the underlying biological mechanisms and treatment.