Psychological states and physical fates: studying the role of psychosocial stress in the etiology of cardiovascular disease: a nomothetic versus an idiographic approach

In this thesis we investigated the theory of allostatic load. This theory has two major hypotheses; 1) that repeated exposure to stress leads to 'wear and tear' of the systems that regulate the bodily response to stress, and 2) that "wear and tear" of these systems leads to disease. In summary, we did not find any relationship between exposure to stress and 'wear and tear' of the stress responsive systems. We did, however, find that cumulative exposure to stressful life-events or having negative emotions is related to an accelerated decrease in telomere length. Telomeres are capping the ends of chromosomes and shorten with each cell division. As a result, telomeres are becoming progressively shorter as people age. Our findings could therefore indicate that people who have a higher exposure to stress or experience more negative emotions are aging more rapidly. Furthermore, we showed that people with a higher resting heart rate are at an increased risk of fatal and nonfatal cardiovascular events. We did not find this to be the case for higher levels of the stress hormone cortisol. Whether this really means that higher cortisol levels do not increase the risk of cardiovascular events remains to be seen. With our repeated measurements study, in which we measured 10 subjects for 63 consecutive days, we demonstrated that levels of salivary and urinary cortisol fluctuate so much on a day-to-day basis within individuals that they cannot be studied in a meaningful way at the group level.