عاطفه مثبت و عملکرد بیولوژیکی در زندگی روزمره

There is accumulating evidence that positive affect may protect against ill–health and risk of disease. Here, we summarize results from our research program into the biological correlates of positive affect. Data have been collected from middle-aged men and women, with positive affect assessed through repeated ratings of happiness over a working day. The results indicate that greater happiness is associated with lower salivary cortisol both on working and nonworking days, reduced fibrinogen stress responses, and lower ambulatory heart rate in men. These effects are independent of age, socioeconomic status, smoking, body mass and psychological distress. A 3 year follow-up has confirmed these biological associations with happiness. In addition, we found that happiness was inversely related to ambulatory systolic blood pressure on follow-up, again independently of potential confounders including negative affect. These results suggest that positive affective states are linked to favorable health outcomes through their influence on health-related biology, and may be particularly relevant in old age, when the accumulation of risk factors leads to increased risk of chronic disease.

There is compelling evidence that negative affective traits, such as depression and anxiety are associated with adverse health outcomes. Longitudinal observational studies have established relationships with cardiovascular disease risk, diabetes, progression of disability, and premature mortality [9] and [15]. A notion that is being increasingly studied is the converse possibility that positive well-being and affect have favorable effects, reducing the rate of premature mortality and the development of various physical illnesses [2] and [7]. Such effects may be particularly relevant to older sectors of the population, among whom aging processes and the accumulation of risk factors lead to a high incidence of chronic disease. The maintenance of positive well-being with advancing years may help protect against in age-related morbidity. If positive affect is associated with good health, the question arises as to which pathways underlie this relationship. This question has lead to research into the biological correlates of positive affect. Some studies have indicated that positive affect is associated with characteristic patterns of electrocortical activation [16], although findings are not entirely consistent [17]. Positive mood in everyday life also appears to be associated with high levels of central serotonergic function [1], a potentially important relationship in view of the links between deficient serotonergic function and higher body mass index (BMI), insulin resistance and blood pressure [5]. Neuroendocrine and immune responses have also been examined as possible mediators of the health effects of positive affect with some positive results [7]. Since positive and negative affect are inversely correlated, the demonstration that positive states are associated with reduced biological responses may be trivial, merely reflecting the absence of negative affect [7]. The conclusions that can be drawn from studies that have measured the biological correlates of positive affect without controlling for negative states are therefore ambiguous. We recently reported an investigation of late middle-aged men and women in which positive affect was associated with lower cortisol, lower heart rate, and reduced fibrinogen stress responsivity [13]. These effects were independent of known confounders, such as age and socioeconomic position, and also of negative mood states as indexed by the General Health Questionnaire (GHQ). In this article, we provide a summary of these findings, then present new data demonstrating the stability of the biological correlates of positive affect over a 3 year period.

This analysis of 3 year follow-up data from our original study group suggests that the associations between biological responses and happiness are quite robust. The cortisol gradient across quintiles of happiness was similar to that observed at Time 1, although the strength of relationship was reduced. The smaller sample size may account in part for this diminution of statistical power. However, the consistency is impressive, bearing in mind that the activities of a typical day had greatly altered over the intervening period for many participants. For example, about 10% had retired during the intervening years. Similarly, the gender difference in the relationship between heart rate and happiness persisted. Raised heart rate is an independent risk factor for mortality and cardiovascular disease, and in the Framingham study was shown to be a more reliable indicator in men than women [4]. Most interesting of all was the emergence of an association between happiness and systolic blood pressure. It should be noted that blood pressure was not measured with casual readings in the clinic, but by averaging up to 35 readings over the day and evening. This increases our confidence in the reliability of the estimate for each individual. The association between greater happiness and lower systolic pressure was independent of factors, such as smoking, body mass and socioeconomic position that are also known to affect pressure levels. It also remained significant after adjustment for negative affect, so was not a reflection of the known relationship between negative affective states and elevated blood pressure [3]. However, we do not know why the effect was not present at the time of initial assessment and only emerged 3 years later. It is possible that advancing aging is responsible. In summary, our findings indicate that positive affect is related to favorable profiles of functioning in several biological systems, and may thereby be relevant to the development of physical illness. We intend that participants in this study will continue to have their health monitored into the future, so we will be able to study relationships between happiness and objective health outcomes as the evolve over the coming years.