and colleagues (2004a, 2004b), which showed that compared to low stress individuals,
the telomeres of individuals with the highest levels of stress were shorter by the
equivalent of at least 10 years of additional ageing! It will be interesting to see how
such effects relate to differences in health behaviours (see e.g. the observations of Khaw
et al., 2008 discussed in Chapter 1) and whether the stress–telomere relationship is
moderated by social support or personality (see Chapters 5 and 6).
As the populations of many developed countries age, the promotion of healthy
ageing has become a public health priority (see e.g. the findings of Yates et al., 2008
in Chapter 1). In this context, understanding the relationship between psychological
factors and endocrine functioning has become important. Recent research, explor-
ing daily cortisol profiles across the lifespan found that older age was associated with
increased daily cortisol secretion throughout the day, which may act as a marker
for psychological and biological vulnerability to adverse health outcomes (Nater,
Hoppmann and Scott, 2013). Similarly, further research is needed to clarify the impact
of other hormones such as testosterone and estrogen, whose production is known to
decline with age, on quality of life outcomes including depression, cognition and sexual
health (e.g. O’Connor et al., 2011b). Further research into physiological functioning
is likely to focus on ‘metabolic syndrome’, a condition that remains somewhat contro -
versial, characterized by obesity, insulin resistance (or type II diabetes), high blood
pressure, high blood triglyceride levels and low levels of high-density lipoprotein
cholesterol. Limited research has thus far indicated that stress-related changes in food
intake, if maintained over time, may play a role in increasing risk of developing
metabolic syndrome (Epel et al., 2004b; Newman et al., 2007).
In Chapter 3 we examined stress using psychological measures (e.g. life events
and daily hassles). Research into stress and individual differences is needed to further
clarify why stressors lead to poor health for some but not for others. Scientific
advances in genetics offer new opportunities to study the role of specific genes in
vulnerability to environmental stressors such as life events (e.g. Power et al., 2013).
Diary studies of daily hassles have recently been used to help elucidate how stressors
influence health behaviours (Bolger and Laurenceau, 2013; Gartland et al., 2014b;
Verkuil et al., 2012). Multi-level statistical techniques have resulted in new
opportunities for data analysis opening up avenues for further research in this area. The
Conservation of Resources theory is a promising theoretical framework focusing on
protective resources, which may help people to be more resistant to stressors while
research into stress recovery may help answer the long-standing question of why some
people get ill in response to stressors and others do not (Adler and Matthews, 1994).
Studies have examined blood pressure and heart rate responses following stressful
encounters. Future research could extend this work by examining whether hormonal
and immunological parameters take longer to return to normal after stress in vulnerable
individuals.
As outlined earlier, recent developments in stress theory have confirmed the
significance of worry, rumination and repetitive thought as important to under-
standing the stress–disease relationships. Brosschot et al.’s (2006) perseverative cognition
hypothesis (PCH) has suggested that worry or repetitive thinking may lead to disease
by prolonging stress-related physiological activation, amplifying short-term responses,
delaying recovery or reactivating responses after a stressor has been experienced.
Recent evidence has demonstrated that perseverative cognition is associated with
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