Acute stress disorder is characterised by the development of severe anxiety, dissociation, and other symptoms that occurs within one month after exposure to an extreme traumatic stressor (e.g., witnessing a death or serious accident). As a response to the traumatic event, the individual develops dissociative symptoms. Individuals with acute stress disorder have a decrease in emotional responsiveness, often finding it difficult or impossible to experience pleasure in previously enjoyable activities and frequently feel guilty about pursuing usual life tasks.

A person with acute stress disorder may experience difficulty concentrating, feel detached from their body, experience the world as unreal or dreamlike, or have increasing difficulty recalling specific details of the traumatic event (dissociative amnesia).

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Acute stress disorder is most often diagnosed when an individual has been exposed to a traumatic event in which both of the following were present:

• The person experienced, witnessed, or was confronted with (e.g., can include learning of) an event or events that involved actual or threatened death or serious injury, or a threat to the physical integrity of self or others.
• Though not required, the person’s response is likely to involve intense fear, helplessness, or horror.

Either during or following the distressing event, the individual has 3 or more of the following dissociative symptoms:

• A subjective sense of numbing, detachment, or absence of emotional responsiveness
• A reduction in awareness of his or her surroundings (e.g., “being in a daze”)
• Derealization
• Depersonalization
• Dissociative amnesia (i.e., inability to recall an important aspect of the trauma)

The traumatic event is persistently re-experienced in at least one of the following ways: recurrent images, thoughts, dreams, illusions, flashback episodes, or a sense of reliving the experience; or distress when exposed to reminders of the traumatic event.

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