cluding assault, rape, and witnessing a mass shooting. 
Development and Course
Acute stress disorder cannot be diagnosed un til 3 days after a traumatic event. Although
acute stress disorder may prog ress to posttraumatic stress di sorder (PTSD) after 1 month,
it may also be a transient stress response th at remits within 1 month of trauma exposure
and does not result in PTSD. Approximately half of individuals who eventually develop
PTSD initially present with acute stress diso rder. Symptom worsenin g during the initial
month can occur, often as a result of ongoin g life stressors or further traumatic events. 
The forms of reexperiencing can vary acro ss development. Unlike adults or adoles-
cents, young children may report frightening dreams without content that clearly reflects
aspects of the trauma (e.g., waki ng in fright in the aftermath of the trauma but being unable
to relate the content of the dream to the traumatic event). Ch ildren age 6 years and younger
are more likely than older children to expres s reexperiencing symptoms through play that
refers directly or symbolically to the trauma. For example, a very young child who sur-
vived a fire may draw pictures of flames. Yo ung children also do not necessarily manifest
fearful reactions at the time of the exposure or even during reexperiencing. Parents typi-
cally report a range of emotional expressions,  such as anger, shame, or withdrawal, and
even excessively bright positiv e affect, in young children who are traumatized. Although
children may avoid reminders of the trauma, they sometimes become preoccupied with
reminders (e.g., a young child bitten by a dog may talk about dogs constantly yet avoid go-
ing outside because of fear of coming into contact with a dog).