Stress and Its Effect on Health

1Exam season

Six weeks before the national examinations, Ishimwe, an S6 student, revises until after midnight, then helps in his family's shop before school. He gets headaches, sleeps badly, snaps at his younger sister and has caught two colds in a month. Nothing terrible has happened to him, yet his body is clearly reacting. This lesson explains what stress is, what it does inside the body, and what the evidence says about its links with illness. (Ishimwe is an illustrative case.)

21. Three ways of defining stress

The transactional model is the one most psychologists use today. It explains why Ishimwe's classmate, who believes she can cope with the same timetable, may feel challenged rather than threatened.

32. Sources of stress

• Life events. Thomas Holmes and Richard Rahe (1967) built the Social Readjustment Rating Scale: 43 life changes, each with a score in "life change units", from death of a spouse (100) through marriage (50) to minor violations of the law (11). In a study of about 2,500 US Navy sailors, Rahe, Mahan and Arthur (1970) found that higher scores went with more illness on a voyage, but the correlation was only +0.118. Evaluation: correlational, so it cannot show cause; relies on memory; treats happy events such as marriage as stressful; ignores the person's appraisal; and several items fit 1960s America better than Rwanda today.
• Daily hassles. Allen Kanner, Richard Lazarus and colleagues (1981) found that small, frequent irritations (losing things, noise, crowded transport, arguments) predicted psychological symptoms better than major life events did. Small pleasant events, uplifts, may partly buffer them.
• Work and school. Robert Karasek's (1979) demand–control model predicts that high demands with little control cause most strain. In the Whitehall II study of British civil servants, Michael Marmot and colleagues (1997) found that people with low control at work had a higher risk of coronary heart disease.
• Frustration and conflict. Frustration arises when a goal is blocked. Following Kurt Lewin, conflicts are classed as approach–approach (two good options: two universities), avoidance–avoidance (two bad options: repeat the year or change school) and approach–avoidance (one option with good and bad sides: a scholarship far from home).
• Chronic and traumatic stressors, such as poverty, discrimination, caring for a sick relative, violence and disasters. These tend to have the largest effects on health.

43. What happens in the body

Walter Cannon (1915) described the fight-or-flight response. Today we describe two linked pathways (Figure 1). The fast SAM pathway prepares the body for action within seconds. The slower HPA axis releases cortisol, which keeps energy available over minutes and hours. Normally cortisol then switches the system off through negative feedback; in chronic stress this control weakens. Shelley Taylor and colleagues (2000) added that people, and women especially, often respond to threat by tending and befriending: protecting children and seeking support, not only fighting or fleeing.

Figure 1. The body's two stress pathways. SAM: sympathetic–adrenal medullary system. HPA: hypothalamic–pituitary–adrenal axis. CRH: corticotropin-releasing hormone. ACTH: adrenocorticotropic hormone.

54. Selye's General Adaptation Syndrome

Hans Selye exposed rats to many different harmful agents (cold, injury, toxins, forced exercise) and found the same pattern of bodily responses, which he called the General Adaptation Syndrome (GAS) (Figure 2):

1. Alarm reaction: the stressor is detected; resistance dips briefly, then the SAM and HPA systems are mobilised.
2. Resistance: the body adapts and resists, with stress hormones kept high; the person may seem to be coping well.
3. Exhaustion: if the stressor continues, the body's resources are worn down and stress-related illness becomes more likely.

Figure 2. Selye's General Adaptation Syndrome. Resistance dips during the alarm reaction, stays above normal while the body resists, and collapses in exhaustion if the stressor continues.

Evaluation. The GAS was a landmark: it linked stress to illness through physiology. But it was based on rats and extreme physical stressors, so generalising to human psychological stress is risky. John Mason (1975) showed that psychological appraisal strongly affects the hormone response, so the response is not as uniform ("non-specific") as Selye claimed. And we now know exhaustion does not mean the body has "run out" of stress hormones; the damage comes from their prolonged effects.

65. Stress and illness: the evidence

The immune system. Janice Kiecolt-Glaser and colleagues (1984) took blood from 75 medical students a month before their exams and on the first day of the exams. The activity of natural killer cells, which fight viruses and tumours, was lower during the exams. In a later study (1995), small standard wounds took about 9 days (24%) longer to heal in women caring for a relative with dementia than in matched controls. Sheldon Cohen, David Tyrrell and Andrew Smith (1991) gave nose drops containing cold viruses to about 400 healthy volunteers: the higher their psychological stress score, the more likely they were to develop a cold, in a dose–response pattern. A meta-analysis of about 300 studies (Segerstrom and Miller, 2004) concluded that brief stressors can actually boost some immune responses, while chronic stressors suppress immunity most.

Evaluate: exam and caregiving studies are natural experiments, so other differences (sleep, diet) may explain the effects; Cohen's experimental design gives stronger evidence of cause.

The heart. Meyer Friedman and Ray Rosenman described a Type A behaviour pattern: competitive, impatient and hostile. In the Western Collaborative Group Study of 3,154 men, Type A men developed coronary heart disease at about twice the rate of the more relaxed Type B men. But a 22-year follow-up (Ragland and Brand, 1988) found that Type A did not predict death from heart disease, and later meta-analyses point to hostility and anger as the harmful element, not the whole Type A pattern.

Indirect effects. Stress also harms health through behaviour: people under stress often sleep less, eat poorly, exercise less, and may start or increase smoking or drinking. Chronic stress is a risk factor for depression and anxiety disorders.

76. Stress and performance

Some arousal helps: a little exam pressure sharpens attention. The Yerkes–Dodson law is usually drawn as an inverted U, with the best performance at moderate arousal and lower performance at very low or very high arousal, especially on complex tasks. Treat it as a rough description: Robert Yerkes and John Dodson's original 1908 study tested how strong electric shocks affected how fast mice learned a discrimination task, not human stress.