To meet the criteria for diagnosis, patients must have been exposed directly or indirectly to a traumatic event, and ≥ 9 of the following must be present for a period of 3 days up to 1 month: Recurrent, involuntary, and intrusive distressing memories of the event Recurrent distressing dreams of the event Dissociative reactions (eg, flashbacks) in which patients feel as if the traumatic event is recurring Intense psychologic or physiologic distress when reminded of the event (eg, by entering a similar location, by sounds similar to those heard during the event) Persistent inability to experience positive emotions (eg, happiness, satisfaction, loving feelings) An altered sense of reality (eg, feeling in a daze, time slowing, altered perceptions) Inability to remember an important part of the traumatic event Efforts to avoid distressing memories, thoughts, or feelings associated with the event Efforts to avoid external reminders (people, places, conversations, activities, objects, situations) associated with the event Sleep disturbance Irritability or angry outbursts Hypervigilance Difficulty concentrating Exaggerated startle response In addition, manifestations must cause significant distress or significantly impair social or occupational functioning and not be attributable to the physiologic effects of a substance-related or another medical disorder.