What Is Acute Stress Disorder?

Acute stress disorder is also sometimes referred to as ‘mental shock’ and describes a psychological condition that occurs in response to highly traumatic events.

Acute stress disorder was first recognized by Walter Cannon in the 1920s and described animals as reacting to threats via a general ‘discharge’ of their sympathetic nervous systems. ASD specifically though describes a more profound reaction than the ‘fight or flight’ response on its own. Rather, it is a more intense response that has longer lasting symptoms and which can potentially develop into more serious conditions such as post traumatic shock.

Symptoms and Cause

The main symptoms of acute stress disorder are:

  • Emotional detachment
  • Muteness
  • Depersonalization
  • Flashbacks
  • Avoidance
  • Amnesia
  • Reliving the event
  • Derealization

Most often these symptoms will be triggered by a highly traumatic, disturbing or terrifying event. Examples include severe pain or injury, perceived severe injury, the death of someone close, sexual assault, physical or mental abuse etc. Normally the symptoms appear within one month of the event itself and can last from two days to a month.

To understand these symptoms better it can be helpful to address the mechanisms of the response and the ‘purpose’.

In a normal stress response, the sympathetic nervous system will release adrenaline, noradrenaline and other hormones via the adrenal glands. These are responsible for all of the usual symptoms that we associate with stress and the ‘fight or flight’ response: such as elevated heart rate, anxiety and heightened awareness. These hormones are called ‘catecholamine’ hormones.

In acute stress disorder however, the response is greater and the psychological impact of the event is increased. The catecholamine hormones also increase the likelihood that we will form memories and mental patterns and in this case they can create deeply ingrained recollections of fear and pain that cause the patient to keep reliving the experience and to continue to experience the negative psychological symptoms.

One of the things that makes acute stress disorder slightly different from post-traumatic shock is the muteness, the depersonalization and the derealization. The exact neurobiological cause of depersonalization and its relationship with stress is not fully understood. What is known however is that similar symptoms such as ‘out of body experiences’ are also often common with panic attacks.

PET scans show functional abnormalities in the visual, somatosensory and auditory areas of the brain. It has also been suggested that it could be a result of hypothalamic-pituitary-adrenal axis dysregulation and patients show unusual levels of cortisol. Interestingly, depersonalization symptoms can also be brought on by cannabis, benzodiazepines and even alcohol.

Either way, it appears that some hormonal change can distance the individual and incur emotional neutrality. From an evolutionary perspective, it’s easy to imagine that being ‘distanced’ from events could help to make them less traumatic and easier to handle where the chance of survival is reduced. It could even increase your chances of survival in situations where struggling and fighting would not be effective. It is also easy to see how subsequent avoidance of similar situations and related factors could hold survival value.

Acute stress disorder, like PTSD, is more common in patients with low levels of cortisol and/or serotonin.


In most cases, acute stress disorder should resolve itself and is self-limiting. However, in cases where patients are constantly reliving their traumatic events, the likelihood of the condition developing into PTSD is increased. Cognitive behavioral therapy along with imaginal and in vivo exposure have been shown to be effective treatments. Anti-depressants and anti-anxiety medications can be useful in treating some cases of acute stress disorder and post traumatic shock but may also exacerbate some symptoms such as derealization.

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