Complex sentence: Symptoms of acute stress disorder are: numbing; detachment; derealization; depersonalization or dissociative amnesia; continued re-experiencing of the event by such ways as thoughts, dreams, and flashbacks; and avoidance of any stimulation that reminds them of the event.
Split into simpler sentences: Symptoms of acute stress disorder are: numbing, detachment, derealization, depersonalization or dissociative amnesia. Continued re-experiencing of the event by such ways as thoughts, dreams, and flashbacks, and avoidance of any stimulation that reminds them of the event.