Health Psychology, 2nd Edition

PERSONALITY AND HEALTH 133

that conscientious individuals appear to be less likely to engage in health-risking
behaviours such as smoking and more likely to engage in health-protective behaviours
such as exercise. As we have already suggested, this might be through exposure to such
behaviours in situations individuals are drawn to. Alternatively, personality traits like
conscientiousness might make some health behaviours more likely by changing the
way conscientious individuals think about behaviours such as exercise (Conner and
Abraham, 2001). Thus conscientious individuals might value health-protective behav -
iours more or might just be better at planning how best to engage in such behaviours.
These cognitions about health behaviours are the focus of Chapter 7.
A final set of explanations for the relationship between personality traits and health
outcomes relates to stress and the variables that protect against the effects of stress. So,
for example, individuals high in neuroticism may perceive themselves as experiencing
more stress. Such individuals may also be less likely to employ appropriate coping
mechanisms or have access to coping resources such as social support to deal with this
stress. In this case it may be the stress that causes the negative health outcomes, but it
is high levels of neuroticism that cause the stress and the inability to cope appropriately
with the stress. Penley and Tomaka (2002) provide an interesting discussion of the
relationship between all of the Big Five personality traits and both stress and coping.
While Ferguson (2013) has proposed a theoretical model explaining the role of per -
son ality in the illness process and identified six routes through which personality can
have an influence on health (see also Bogg and Roberts, 2013 for a discussion of
conscientiousness and health).

Correlation and inferences of causation

When an independent (or predictor) variable (e.g. social support or attitude) is

measured at the same time as a dependent (or outcome) variable (e.g. immune

functioning or condom use) this is known as a cross-sectional study. When the

dependent variable is measured at a later time then this is known as a longitudinal or

prospective study. For example, if we measure job stress and then follow up our

participants a year later this is a prospective study. Prospective studies offer more

reassurance regarding the direction of causation because we know that the

independent variable measure preceded the dependent variable measure in time.

Prospective studies also allow us to control for levels of a dependent variable at time

1 so that we can predict change in the dependent variable from an independent

variable. For example, we might find that lower reported social support (at time 1)

predicts increases in stress over the following year (i.e. changes from time 1 to time

2). Thus while we might use analysis of variance (ANOVA) to test whether an

association between an independent and dependent variable is likely to be replicable,

we can use analysis of covariance (ANCOVA) to assess the degree to which an

independent variable can predict change in a dependent variable over time by

including a baseline measure of the dependent variable as a covariate.

RESEARCH METHODS 6.1