Posttraumatic stress disorder, or PTSD, is a collection of negative behaviors, symptoms, and moods triggered by a traumatic experience. PTSD can also be triggered by an ongoing event. The event can occur over a matter of days, weeks, months, or even years. This is known as complex posttraumatic stress disorder or C-PTSD. Experiences associated with posttraumatic stress disorder are abuse, terrorism, natural disasters, violence, and illness.