Health Psychology : a Textbook

Interaction between the behavioural and physiological pathways

Stress can therefore influence health and illness by changing behaviour or by directly

impacting upon an individual’s physiology. So far the behavioural and physiological

pathways have been presented as separate and discrete. However, this is very much an

oversimplification. Stress may cause changes in behaviours such as smoking and diet

which impact upon health by changing the individual’s physiology. Likewise, stress may

cause physiological changes such as raised blood pressure but this is often most apparent

in those that also exhibit particularly unhealthy behaviours (Johnston 1989). Therefore,

in reality, stress is linked to illness via a complex interaction between behavioural

and physiological factors. Further, Johnston (1989) argued that these factors are multi-

plicative, indicating that the more factors that are changed by stress the greater the

chance that stress will lead to illness.

INDIVIDUAL VARIABILITY IN THE STRESS–ILLNESS LINK

Not everyone who experiences stress becomes ill. To some extent this is due to the role

of variables such as coping, control, personality and social support which are described

in detail later on. However, research indicates that this variability is also due to

individual differences in stress reactivity, stress recovery, the allostatic load and stress

resistance.

Stress reactivity

Some individuals show a stronger physiological response to stress than others which

is known as their level of ‘cardiovascular reactivity’ or ‘stress reactivity’. This means

that when given the same level of stressor and regardless of their self perceived stress

some people show greater sympathetic activation than others (e.g. Vitaliano et al. 1993).

Research suggests that greater stress reactivity may make people more susceptible to

stress-related illnesses. For example, individuals with both hypertension and heart

disease have higher levels of stress reactivity (e.g. Frederickson and Matthews 1990;

Fig. 11-3 The stress–illness link: physiological moderators

258 HEALTH PSYCHOLOGY