Index:
- Autonomic Nervous System (ANS), SAM and HPA
- General Adaptation Syndrome (GAS)
- Stress on heath
- Stress through life changes
- Daily hassles
- Evaluation of the studies
AUTONOMIC NERVOUS SYSTEM (ANS), SAM and HPA
The ANS is a part of the Nervous System which serve the task of controlling involuntary actions, such as the functioning of organs. It is subdivided into the Sympathetic and Parasympathetic Nervous Systems (SNS and PsNS). The SNS is involved in the fight or flight response, which prepares the organism for a reaction to a danger, be it by fighting it or escaping from it (i.e. running), and when this is over, the PsNS will make everything go back to normal.
SAM is the sympathomedullary pathway, and it is the response to immediate stressors. When a danger is detected by the senses, the SNS (S) alerts the adrenal medulla (M) through signals sent via the Central Nervous System (CNS) - which consists of the brain and the spinal-chord. The adrenal medulla is the middle part of the adrenal gland, located just above the kidneys, and in response to this signal it will secrete adrenaline and noradrenaline (A). These hormones will travel through the bloodstream, stimulating specific organs. For example, the heart will beat faster to pump more blood, respiration will accelerate in order to have more oxygen in the blood, and blood pressure increases so that muscles get more energy that readies them to respond to a threat.
SNS > CNS > adrenal medulla > adrenaline and noradrenaline > fight or flight
The HPA is the response that the body has for long term or ongoing stressors, and it stands for hypothalamic pituitary-adrenal axis. Like the SAM, it begins activating the SNS, specifically the hypothalamus (H), which is located in the brain, close to the amygdalas. The hypothalamus secretes corticotrophin-releasing hormone (CRH), which travels to the pituitary gland (P), also known as the mother gland of the endocrine system*, and stimulates it to produce adrenocorticotrophin hormone (ACTH). The ACTH hormone will travel through the bloodstream and stimulate the adrenal cortex (A), which will release various stress related hormones, including cortisol, which, if out in the brain for too long, can literally shrink its size.
Hypothalamus > CRH > pituitary gland > ACTH > adrenal cortex > stress-related hormones
*Endocrine system: the system formed by all the glans in the body. The hypothalamus is the sensory register that connects it to the real world, and the pituitary gland is called its mother gland because from it the instructions of the hypothalamus are communicated to all other glands.
GENERAL ADAPTATION SYNDROME (GAS)
The Hungarian researcher Hans Selye was the proposer of this model. It is divided into three stages:
Stage 1 is where the hypothalamus detects the danger and the SNS is activated. This leads to Stage 2, in which the body will be in the fight or flight response. Here the adrenal gland is secreting adrenaline and noradrenaline to provide energy to the muscles. However, it is when the stressor elongates for long periods that we enter Stage 3. Throughout Stage 2, the organism has adapted to the environment, meaning that, in the knowledge that some kind of danger is imminent, the adrenal gland perpetually secretes stress-related hormones, to maintain the body in a stable state of readiness. However, to do this it needs of resources - sugars, proteins, neurotransmitters, hormones - and when these run out, the individual will again experience the initial symptoms of stress, including dizziness, exhaustion, sweating. Selye proposes that further damage to the health is caused by damage to the adrenal gland, which is now like an old car engine: overused and exhausted. However, Sheridan & Radmacher found that the body does not at any point run out of resources (given diet is maintained steadily), but in Stage 3 the adrenal gland begins to work faster and it is this overuse of it that causes harm, including ulcers or psychological issues such as depression.
STRESS ON HEALTH
Kiecolt-Glaser found that ongoing stress has a negative effect on the immune system. Natural Killer cells (NKs) are a type of white blood cells that detect and destroy antigens such as viruses. In her study of 1984 (Kiecolt-Glaser et al), she took a sample of 75 medical students, and took two blood samples: one a month before their exams (low stress) and one during their exam period (high ongoing stress). She also had them complete a Social Readjustment Rating Scale (SRRS)* to measure their general levels of stress and a loneliness scale to assess their social circles. They found that for all student, there were less NKs in the second blood sample, and the effect was worse for those who had scored high in the SRRS and the loneliness scale. This suggests that there is a correlation between life change, healthy relationships and ongoing stressors with the immune system.
*The SRRS is a scale that lists a series of events that would change significantly a person's life, such as the death of a spouse or close relative, or being fired from work. Each event has a life change unit (LCU) attached to it. These are like points. Death of a relative gives 100 LCUs, while being fired from work gives 47. It is completed for an agreed time period, for example for events within the last three months.
Furthermore, Williams et al (2000) investigated the effects of anger of cardiovascular health. Like stress, anger activates the Sympathetic Nervous System (SNS). In their study they had 13 000 complete an anger scale, asking them to describe how they acted when angry - the questions explored whether the person got annoyed when not given recognition for some accomplishment, or whether they had violent thoughts when they were angry. Six years later, they found that 256 out of the 13 000 people had had heart attacks, and there was an important positive correlation between score in the anger scale and likelihood to be in this group. People who scored high were up to 2'5 time more likely to suffer a heart attack.
LIFE CHANGE
Rahe & Kanner et al conducted a study on US Navy officials with a variant of the SRRS called Schedule of Recent Events (SRE). In this questionnaire they were asked to self-report about their life for the past two years (the SRE was adapted to be relevant for their profession). This was done just before they boarded on a trip for 8 months overseas, and during this time each was monitored on how many times they attended the sick bay and how severe their illness was. They found that frequency of visits and severity of illness was positively correlated to SRE score. The SRE includes not only negative events, such as the explained above in the SRRS* section, but also positive ones like Christmas. This suggests that stress is not only caused by negative things, but can stem from the simple change of lifestyle. For example, a parent will get stress from having to find time to buy Christmas presents for his or her children. This is due to what they called psychic energy, which is extra mental and emotional effort.
DAILY HASSLES
These are minor stressors in everyday life, like traffic on your way to work, but evidence suggests that daily hassles actually more impact on levels of stress than major life changes. Kanner and Lazarus et al (1981) conducted a study in which 100 participants, male and female, took an SRRS of the past six months, and every month for the next 9 months they took a Hassles and Uplifts scale (HSUP). At the end of the 9 months they took another SRRS and two scales measuring their psychological well-being (Hopkins Symptom Checklist and Bradburn Morale Scale). They found that the correlation between hassles and well-being was much more important than that between life-change and well-being. Moreover, hassles were a better predictor of well-being than uplifts. Flett et al (1995) suggest that this might be due to hassles attracting less moral support than major life-changes. Lazarus argues that daily hassles generate large stress because they accumulate over time. Another explanation for this phenomenon is amplification, where someone who is undergoing a life-change becomes more sensitive to minor hassles. For example, a worker who has just divorced is likely to be more disturbed by inconveniences due to traffic than he or she normally would.
EVALUATION OF THE STUDIES
Most of these studies are correlational, rather than focusing of causation. This means that they only find that when A happens, B tends to happen. They tell us nothing of whether A causes B or B causes A or if C causes both B and A. It could be that those who reported more negative events turned out as the ones who presented more symptoms of depression and anxiety because being depressed and anxious gave them a negative worldview and they remembered more the negative things that happened.
There are a number of individual differences. For example, the SNS is not equally sensitive for all people, and thus some might have more dramatic responses of the adrenal medulla from the same stressor. In this way, Lazarus and Folkman (1984) argue that there is a cognitive stage before any response to danger is enacted. In this stage, the individual assesses and compares the perceived demands and his or her perceives ability to meet them, in such way that if an individual feels able to overcome the danger, there will be no response, or a lesser one. Taylor et al (2000) found that females respond differently to danger than males. They don't use the fight-or-flight response, but rather a tend-and-befriend approach. They suggest that this might be due to a desire to keep violence away from their offspring. Until then, most research on the topic had been done on male non-human animals, because it was a concern that hormonal cycles in females might affect negatively the validity of studies.
Furthermore, the SRRS has been criticised because not everyone will value and be affected in the same way by the life changes listed, so a point system is too simplistic. For example, being fired from work affects differently a person who liked their job and feels unable to find another one compared to someone who hated their job and think they will be employed soon in something else. More methodological issues concern the use of self-report techniques, which are methods where the participants report about themselves, as in questionnaires. For a start, these always run the risk of being biased, because they are subjective and vulnerable to social desirability - the participant modifies their answers to match what's socially acceptable or praised. This reduces their validity, but there is also a problem with reliability. Lazarus (1995) conducted test re-test* on SRRS and found that the longer the period participants had to report about, the lower the reliability/consistency of their answers, because the method relies heavily on memory.
*Test re-test is a way to measure the reliability of a research method which involves giving participants the test one first time and then retaking it after a time-lapse sufficient for them to have forgotten their answers, for example three weeks.
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