Stress is generated when we encounter a situation, posing a real or perceived threat, which we feel unable to deal with (Alder et al 2004). These threats are known as ‘stressors’ which can be categorised as internal or external.
The effect of a stressor can be acute or chronic. During an acute stress response, where the body has been placed in a traumatic situation, real or perceived, there is a preparation to deal with the situation, this is called the ‘fight or flight response’ (Cannon 1929, cited in Sarafino 2006), where the person will either deal with the threat head on, or run away. Cannon’s fight or flight response was later integrated into the first stage of the General Adaption Syndrome (GAD) (Selye 1956 cited in Ogden 2000)
Figure 1. Selye’s three stage general adaption syndrome adapted from Ogden (2000)
During the alarm phase, a reaction of the sympathetic nervous system (SNS) stimulates a nervous and hormonal response, this trigger’s activation of the hypothalmic-adrenal-axis where the hypothalamus stimulates the release of ACTH, causing the release of epinephrine (adrenaline), noradrenaline and cortisol from the adrenals. As neurotransmitters, epinephrine and noradrenaline cause; an increase mental alertness, raise the heart and breathing rate, cause vasoconstriction of blood vessels to the skin and digestive organs and vasodilation to the large muscle groups, raise glycogen levels and restrict digestion and urine production (Martini & Nath 2009).
Increased cortisol levels in the blood will raise blood pressure, interfere with insulin production causing hyperglycemia, give an initial boost to the immune system but suppress it over longer periods of time.
If the stressor continues, the body aims to adapt and enters the resistance phase. Cortisol and epinephrine levels will remain elevated in the blood and the body will find it harder to respond to new stresses. There will be an increased energy demand on the body, due to the combined effects of these hormones so glucose will be metabolised for energy from fat stores in the body. Chronic levels of stress will have serious side effects over long periods. As observed by McEwan (2000), this cumulative effect of stress over a long period of time can be termed allostatic load and increases susceptibility to certain diseases later in life such as cardiovascular disease which can be linked to high blood pressure and increased cholesterol levels (both an effect of elevated cortisol).
When the body has used all its reserves it enters the exhaustion stage. Immunity is impaired as cortisol suppresses the proliferation of T-cells making us more susceptible to infectious diseases (Cohen, Tyrrell & Smith 1993). If there is no respite from the stressor, the body will incur irreversible damage to internal systems which can no longer maintain homeostasis and eventual outcome will be death.
Psychological changes also take place when a stressor is introduced. General cognitive functioning, including perception, memory processes and decision making can all be impaired as our attention is directed to the stressor. Important information can be forgotten during times of stress (Sutton, Baum & Johnston 2004), while stressful experiences can be enhanced in peoples memories due to the presence of epinephrine and norepinephrine (Sarafino 2006).
Emotions associated with stress can include distress, fear, excitement, anger and depression. Presence of these emotions may continue even after the stressor has been removed leading to anxiety, which can be defined as a general feeling of unease, apprehension or worry. It can be categorized in the following ways:
- Phobias are a disproportional fear of something which isn’t a real threat.
- Generalised anxiety is a feeling of unease with no known source.
- Panic attacks occur with an acute and intense onset of anxiety symptoms, where the person may be overwhelmed by fear or loss of control.
- Obsessive-compulsive disorder (OCD) causes the individual to have recurrent and intrusive thoughts which they try to minimise by carrying out certain repetitive behaviors.
- Post-traumatic and acute stress can occur after an extreme traumatic event, such as rape, war, RTA. The individual relives these experiences through flash-backs or nightmares along with a constant feeling of arousal. (Davison & Neale 2001)
It is important to note that the physical and psychological impact’s of stress are inextricably linked through interactions of our nervous and endocrine systems. Stressors can affect people in different ways as everyone has their own stress threshold which is predicted by their personal characteristics, situation, past experiences and coping mechanisms (McVicar 2003). This implies that for a given stressor one person may have an increased quality of functioning and another may be suffering any of the extremes of stress or anxiety described above, this is demonstrated by Hebb’s (1955) quality of functioning model, where functioning increases to an optimal level with an increase in stress giving a positive effect but thereafter functioning decreases as stress continues to increase.
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