After a life-threatening event, a person continues to re-experience the trauma through intrusive memories, nightmares, and flashbacks, while avoiding reminders and remaining hyper-alert. Post-traumatic stress disorder, or PTSD, is that constellation of persistent symptoms.

Not everyone exposed to trauma develops PTSD; risk depends on the nature of the event, prior vulnerability, peri-traumatic reactions, and post-event support. Symptoms are grouped into intrusion, avoidance, negative alterations in cognition and mood, and alterations in arousal and reactivity. The disorder can appear after combat, assault, disasters, or accidents.

Trauma-focused cognitive-behavioral therapies, including prolonged exposure and cognitive processing therapy, have strong evidence. EMDR is also widely used. Medication can address specific symptoms. Early intervention and social support improve prognosis. PTSD shows how a single event can reorganize memory, attention, and the sense of safety for years afterward.

Recovery involves reclaiming the present from the repeated intrusion of the past.