Introduction The physical consequences of critical illness are relatively easily recognized by clinicians, families and patients. Less apparent are psychological symptoms that appear during critical illness and afterwards and that can combine to create symptom clusters of sufficient severity that a specific psychiatric disorder results. Recognizing the psychological symptoms that are expected after major illness and knowing the usual severity and duration of symptoms is an important skill for clinicians caring for patients during and after critical care. Almost all psychiatric research on the epidemiology and treatment of depression, anxiety or post-traumatic stress disorder (PTSD) has been conducted with patients not in critical care units, so that translating research from ambulatory patients with little medical comorbidity to critically ill patients is difficult. No clinical recommendations can be made that are supportedby multiple trials performedin critical care patients.