Acute stress reaction (also called acute stress disorder, psychological shock, mental shock, or simply shock) is a psychological condition arising in response to a terrifying or traumatic event, or witnessing a traumatic event that arises a strong emotional response within the indivdual. It should not be confused with the unrelated circulatory condition of shock/ hypoperfusion, or the concept of shock value. Acute stress reaction may develop into delayed stress reaction or better known as PTSD if stress isn't correctly managed.
"Acute stress response" was first described by Walter Cannon in the 1920s as a theory that animals react to threats with a general discharge of the sympathetic nervous system. The response was later recognized as the first stage of a general adaptation syndrome that regulates stress responses among vertebrates and other organisms.
Signs and symptoms
Common symptoms that sufferers of acute stress reaction experience are: numbing; emotional detachment; muteness; derealization; depersonalization; psychogenic amnesia; continued re-experiencing of the event via thoughts, dreams, and flashbacks; and avoidance of any stimulation that reminds them of the event. During this time, they must have symptoms of anxiety, and significant impairment in at least one essential area of functioning. Symptoms last for a minimum of 2 days, and a maximum of 4 weeks, after which point continued symptoms may result in a diagnosis of PTSD.
Acute stress disorder (abbreviated ASD, and not to be confused with autism spectrum disorder) is the result of a traumatic event in which the person experiences or witnesses an event that causes the victim/witness to experience extreme, disturbing, or unexpected fear, stress, or pain, and that involves or threatens serious injury, perceived serious injury, or death to themselves or someone else. A study of rescue personnel after exposure to a traumatic event showed no gender difference in acute stress reaction. Acute stress reaction is a variation of post-traumatic stress disorder (PTSD).
The onset of an acute stress response is associated with specific physiological actions in the sympathetic nervous system, both directly and indirectly through the release of adrenaline and to a lesser extent noradrenalinefrom the medulla of the adrenal glands. These catecholamine hormones facilitate immediate physical reactions by triggering increases in heart rate and breathing, constricting blood vessels. An abundance of catecholamines at neuroreceptor sites facilitates reliance on spontaneous or intuitive behaviors often related to combat or escape.
Normally, when a person is in a serene, unstimulated state, the "firing" of neurons in the locus ceruleus is minimal. A novel stimulus, once perceived, is relayed from the sensory cortex of the brain through the thalamus to the brain stem. That route of signaling increases the rate of noradrenergic activity in the locus ceruleus, and the person becomes alert and attentive to the environment.
If a stimulus is perceived as a threat, a more intense and prolonged discharge of the locus ceruleus activates the sympathetic division of the autonomic nervous system (Thase & Howland, 1995). The activation of the sympathetic nervous system leads to the release of norepinephrine from nerve endings acting on the heart, blood vessels, respiratory centers, and other sites. The ensuing physiological changes constitute a major part of the acute stress response. The other major player in the acute stress response is the hypothalamic-pituitary-adrenal axis.
The autonomic nervous system controls all automatic functions in the body and contains two subsections within it that aids in response to an acute stress reaction. these two subunits are the sympathetic nervous system and the parasympathetic nervous system. The sympathetic response is colloquially known as the "fight or flight" response, indicated by accelerated pulse and respiration rates, pupil dilation, and a general feeling of anxiety and hyper-awareness. This is caused by the release of epinephrine and norepinephrine from the adrenal glands. the norepinephrine and epinephrine strike the beta receptors of the heart in order to feed the heart sympathetic nerve fibers to increase the strength of heart muscle contraction. as a result more blood is being circulated increasing the heart rate and respiratory rate. The sympathetic nervous system also stimulates the skeletal system and muscular system in an effort to pump more blood to those areas to handle the acute stress. simultaneously the sympathetic nervous system inhibits the digestive system and the urinary system in order to optimize blood flow to the heart, lungs, and skeletal muscles. this plays a role in the alarm reaction stage. The para-sympathetic response is colloquially known as the "rest and digest" response, indicated by reduced heart and respiration rates, and more obviously by a temporary loss of consciousness if the system is fired at a rapid rate. The parasympathetic nervous system stimulates the digestive system and urinary system in order to send more blood to those systems to increase the process of digestion. In order to do this, it must inhibit the cardiovascular system and respiratory system in an effort to optimize blood flow to the digestive tract causing low heart and respiratory rates. parasympathetic plays no role in acute stress response (VanPutte Regan Russo 2014). 
There must be a clear temporal connection between the impact of an exceptional stressor and the onset of symptoms; onset is usually within a few minutes or days but may occur up to one month after the stressor. In addition, the symptoms show a mixed and usually changing picture; in addition to the initial state of "daze," depression, anxiety, anger, despair, overactivity, and withdrawal may all be seen, but no one type of symptom predominates for long; the symptoms usually resolve rapidly in those cases where removal from the stressful environment is possible; in cases where the stress continues or cannot by its nature be reversed, the symptoms usually begin to diminish after 24–48 hours and are usually minimal after about 3 days.
If symptoms last for more than a month, then the patient might be instead diagnosed with PTSD.
This disorder may resolve itself with time or may develop into a more severe disorder such as PTSD. However, results of Creamer, O'Donnell, and Pattison's (2004) study of 363 patients suggests that a diagnoses of acute stress disorder had only limited predictive validity for PTSD. Creamer et al. did find that re-experiences of the traumatic event and arousal were better predictors of PTSD. Medication can be used for a short duration (up to four weeks).
Studies have been conducted to assess the efficacy of counselling and psychotherapy for people with ASD. Cognitive behavioral therapy which included exposure and cognitive restructuring was found to be effective in preventing PTSD in patients diagnosed with ASD with clinically significant results at 6 months follow-up. A combination of relaxation, cognitive restructuring, imaginal exposure, and in vivo exposure was superior to supportive counseling. Mindfulness based stress reduction programs also appear to be effective for stress management.
In a wilderness context where counseling, psychotherapy, and cognitive behavioral therapy is unlikely to be available, the treatment for acute stress reaction is very similar for the treatment of cardiogenic shock, vascular shock, and hypovolemic shock; that is, allowing the patient to lie down, providing reassurance, and removing the stimulus for the occurrence of the reaction. In traditional shock cases, this is generally the relieving of pain from injuries or the stopping of blood loss. In an acute stress reaction, this may be pulling a rescuer away from the emergency to calm down, or blocking the sight of an injured friend from a patient.