What is post-traumatic stress disorder (PTSD) and what are its key symptoms?

PTSD (DSM-5) develops in some individuals exposed to trauma — actual or threatened death, serious injury, or sexual violence. Exposure types: directly experiencing, witnessing, learning about (close family/friend), or repeated/extreme exposure (first responders). Symptoms persist >1 month and cause significant distress/impairment. Four symptom clusters (1+ from each cluster required): (1) INTRUSION — recurrent, involuntary memories; nightmares; flashbacks (dissociative reactions where the person feels they are re-experiencing); intense psychological distress at trauma cues; physiological reactivity to trauma cues. (2) AVOIDANCE — efforts to avoid trauma-related memories/thoughts/feelings; efforts to avoid external reminders (people, places, situations). (3) NEGATIVE ALTERATIONS in cognition/mood — inability to remember important aspects of trauma; persistent negative beliefs ('I'm bad,' 'No one can be trusted'); distorted blame; persistent negative emotional state; diminished interest in activities; detachment; inability to experience positive emotions. (4) AROUSAL AND REACTIVITY — irritability/anger outbursts; reckless or self-destructive behavior; hypervigilance; exaggerated startle; concentration problems; sleep disturbance. Subtypes: with dissociative symptoms; with delayed expression (symptoms develop 6+ months later). Acute Stress Disorder: similar to PTSD but lasts 3 days to 1 month. Treatment: (1) Trauma-focused therapy — Prolonged Exposure (PE), Cognitive Processing Therapy (CPT), EMDR (Eye Movement Desensitization and Reprocessing) — gold standard treatments; (2) Medications — SSRIs (sertraline, paroxetine FDA-approved); SNRIs (venlafaxine); prazosin for nightmares; (3) Group therapy; (4) Mind-body practices — yoga, mindfulness; (5) Service animals. Nursing care: trauma-informed approach throughout; recognize triggers; safety; therapeutic alliance.