The person has been exposed to a traumatic event in which both of the following were present:

The person experienced, witnessed, or was confronted with an event
    or events that involved actual or threatened death or serious injury, or
    a threat to the physical integrity of self or others.

The person's response involved intense fear, helplessness, or horror.

Either while experiencing or after experiencing the distressing event, the individual has three (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").

Depersonalization - dissociative amnesia (i.e., inability to recall an important aspect of the trauma).

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

Marked avoidance of stimuli that arouse recollections of the trauma (e.g., thoughts,
    feelings, conversations, activities, places, people).

There are marked symptoms of anxiety or increased arousal (e.g., difficulty
   sleeping, irritability, poor concentration, hypervigilance, exaggerated startle
   response, motor restlessness).

At least 1of the following applies:

The patient feels marked distress from the symptoms.

They interfere with usual social, job or personal functioning.

They block the patient from doing something important such as getting legal or medical help or telling family or other supporters about the experience.

The disturbance lasts for a minimum of 2 days and a maximum of 4 weeks
   and occurs within 4 weeks of the traumatic event.

The disturbance is not due to the direct physiological effects of a substance
   (e.g., a drug of abuse, a medication) or a general medical condition, is not
    better accounted for by Brief Psychotic Disorder, and is not merely an
    exacerbation of a preexisting mental disorder.

Associated Features:

These symptoms may occur and are more commonly seen in association with an interpersonal stressors such as childhood sexual or physical abuse, domestic violence, impaired affect, self-destructive and impulsive behavior, dissociative symptoms, somatic complaints or a change from the individual’s previous personality characteristics.

Differential Diagnosis:

Some disorders display similar or sometimes even the same symptom. The clinician, therefore, in his diagnostic attempt has to differentiate against the following disorders which one needs to be ruled out to establish a precise diagnosis.

Mental Disorder Due to a General Medical Condition;
Substance-Induced Disorder;
Brief Psychotic Disorder;
Major Depressive Episode;
Posttraumatic Stress Disorder;
Adjustment Disorder;
Malingering.    

Cause:

When an individual who has been exposed to a traumatic event develops anxiety symptoms, re-experiencing of the event, and avoidance of related stimuli lasting less than four weeks they may develop acute stress disorder.

Treatment:

Counseling and Psychotherapy

Anxiety disorders are responsive to counseling and to a wide variety of psychotherapies. More severe and persistent symptoms also may require pharmacotherapy.

Psychotherapies include focused, time-limited therapies that address ways of coping with anxiety symptoms more directly rather than exploring unconscious conflicts or other personal vulnerabilities  These therapies typically emphasize cognitive and behavioral assessments.

It is possible that more traditional forms of therapy based on psychodynamic or interpersonal theories of anxiety also may be used However, these therapies have not yet received extensive empirical support

Pharmacotherapy

Antidepressants:
Clomipramine

Benzodiazepines:
Alprazolam;
Clonazepam
Diazepam
Lorazepam

SSRI class:
Fluoxetine
Sertraline
Paroxetine
Fluvoxamine
Citalopram

Combinations of Psychotherapy and Pharmacotherapy:

Some patients with this disorder may benefit from both psychotherapy and pharmacotherapy treatment modalities, either combined or used in sequence