Stress

The physiology of stress

Stress happens when we think the demands on us are bigger than our ability to cope. A stressor is the event that causes it. The body responds in two ways.

Acute (short-term) stress: the SAM pathway (sympathomedullary). The hypothalamus activates the sympathetic nervous system, which signals the adrenal medulla to release adrenaline (and noradrenaline). In seconds: heart rate and blood pressure rise, breathing speeds up, glucose is released, digestion slows. This is fight or flight. When the threat passes, the parasympathetic system calms the body ('rest and digest').

Chronic (long-term) stress: the HPA axis. The hypothalamus releases CRH → the pituitary gland releases ACTH → the adrenal cortex releases cortisol. Cortisol keeps energy available and lowers pain, but long-term high cortisol weakens the immune system and can affect memory. Negative feedback: high cortisol tells the hypothalamus and pituitary to slow down.

Stress and illness

Immunosuppression: stress lowers the immune system's ability to fight disease. In a well-known study, medical students' natural killer (NK) cell activity was lower during exams than a month before. Other studies found that wounds healed more slowly in stressed carers and in couples after arguments.

Cardiovascular disorders: repeated SAM activation raises blood pressure and heart rate. Over time this can damage blood vessels and is linked to high blood pressure, heart attacks and stroke. For example, studies found people with high anger or long work stress had more heart problems.

Evaluation: most studies are correlational; stress may also change behaviour (poor sleep, smoking, less exercise), which harms health indirectly. Short-term stress can actually boost some immune responses.

Sources of stress and how to measure it

• Life changes: big events that need adjustment, good or bad (death of a loved one, marriage, moving). The Social Readjustment Rating Scale (SRRS) gives each event Life Change Units (LCUs). Classic research found higher LCU totals linked with more illness the following year.
• Daily hassles: small, frequent irritations (traffic, lost keys, arguments). Hassles may predict health better than life changes because they add up. Uplifts (small pleasures) can offset them. Measured with the Hassles and Uplifts Scale.
• Workplace stress: workload (too much to do) and control (little say over how to work). Studies of civil servants found those with low job control had more heart disease.

Physiological measure: the skin conductance response (SCR): stress makes skin sweat slightly, so it conducts more electricity. It is objective, but can be affected by other things like heat.

Individual differences: personality and hardiness

• Type A: time pressure, competitiveness, hostility. Early research linked Type A to heart disease; later work suggests hostility is the key risk factor.
• Type B: relaxed, patient, less competitive.
• Type C: pleasant, hides negative feelings; tentatively linked to cancer, but evidence is mixed.
• Type D ('distressed'): high negative feelings plus social inhibition (keeps them hidden); linked to poorer heart health.
• Hardiness: the 3 Cs: control (I can influence my life), commitment (involvement in work and people) and challenge (change is a chance to grow). Hardy people seem less affected by stress, and hardiness can be trained.

Managing and coping with stress

Drug therapy: benzodiazepines increase the effect of GABA, the brain's calming chemical. Beta-blockers block adrenaline's effects on the heart and blood vessels (used for performance anxiety). Quick and easy, but treat symptoms only, have side effects and can cause dependence (benzodiazepines).

Stress inoculation training (SIT), like a vaccine: (1) conceptualisation: understand your stress and reframe it; (2) skills acquisition and rehearsal: relaxation, positive self-talk, assertiveness, time management; (3) real-life application: use the skills in gradually harder situations. It deals with causes, but takes time and effort.

Biofeedback: sensors show heart rate or muscle tension on a screen. The person learns relaxation and sees it work (reinforcement), then uses it in daily life. Needs equipment and practice.

Gender differences: women may more often show a 'tend and befriend' response (care for others, seek support), linked to oxytocin; men more often fight or flight.

Social support: instrumental (practical help), emotional (care, listening) and esteem (building confidence). People with strong support often have better immune function and lower stress.

Try it

In step 5, tap the events that happened to you or a made-up person this year and watch the LCU total. Then for one week, write down three hassles and three uplifts each day. Do uplifts make the hassles feel smaller? Try 5 minutes of slow breathing when stressed: you are practising a skill from SIT.

Key formulas and definitions

• Key term: SAM pathway = hypothalamus → sympathetic nervous system → adrenal medulla → adrenaline (acute)
• Key term: HPA axis = hypothalamus (CRH) → pituitary (ACTH) → adrenal cortex (cortisol) (chronic)
• Key term: Immunosuppression = weakened immune system due to stress
• Key term: Life Change Units (LCU) = scores for life events on the SRRS
• Key term: Daily hassles and uplifts = small negative and positive daily events
• Key term: Hardiness = Control, Commitment, Challenge
• Key term: SIT = conceptualisation → skills acquisition → application
• Key term: Social support = instrumental, emotional, esteem

Worked examples

Common mistakes

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