Posttraumatic stress disorder (PTSD) is a mental health condition that develops after exposure to a traumatic event. Symptoms include re-experiencing the trauma through flashbacks or nightmares, avoidance of trauma-related stimuli, increased arousal and negative changes in mood and cognition. Risk factors include a history of childhood trauma, lack of social support, and severity of the traumatic event. Effective treatments include trauma-focused cognitive behavioral therapy and medications like SSRIs.