Positive affect and health-related neuroendocrine, cardiovascular, and inflammatory processes
Andrew Steptoe,* Jane Wardle, and Michael Marmot
International Centre for Health and Society, Department of Epidemiology and Public Health, University College London, London WC1E 6BT, United Kingdom
Edited by Bruce S. McEwen, The Rockefeller University, New York, NY, and approved March 8, 2005
Received December 9, 2004.
Negative affective states such as depression are associated with premature mortality and increased risk of coronary heart disease, type 2 diabetes, and disability. It has been suggested that positive affective states are protective, but the pathways through which such effects might be mediated are poorly understood. Here we show that positive affect in middle-aged men and women is associated with reduced neuroendocrine, inflammatory, and cardiovascular activity. Positive affect was assessed by aggregating momentary experience samples of happiness over a working day and was inversely related to cortisol output over the day, independently of age, gender, socioeconomic position, body mass, and smoking. Similar patterns were observed on a leisure day. Happiness was also inversely related to heart rate assessed by using ambulatory monitoring methods over the day. Participants underwent mental stress testing in the laboratory, where plasma fibrinogen stress responses were smaller in happier individuals. These effects were independent of psychological distress, supporting the notion that positive well-being is directly related to health-relevant biological processes.
Keywords: cortisol, well-being, fibrinogen, heart rate
Proc Natl Acad Sci U S A. 2005 May 3; 102(18): 6508–6512. By 2005, The National Academy of Sciences.
There is growing evidence that affective states are associated with physical health. A metaanalysis of 25 prospective studies of adults with follow-up periods ranging from 2 to 16 years showed a consistently increased risk of mortality for both clinical and subclinical depression (1). Negative affective states such as depression are associated with increased risk of coronary heart disease, type 2 diabetes, and disability (2-4). Research in positive psychology is beginning to identify effects of psychological well-being on health as well (5, 6). For example, Danner et al. (7) reported a longitudinal analysis of a sample of Catholic nuns, in which the positive emotional content of writings at the age of 22 was associated with longevity during a 60-year period. A negative relationship between life satisfaction and mortality has been described in a 20-year study of initially healthy Finnish adults that was independent of marital status and social class (8). Whittington and Huppert (9) showed that 7-year mortality in a British cohort was more consistently associated with the absence of positive well-being than with the presence of symptoms of psychological distress. Other studies have reported that a lack of positive affect rather than heightened negative affect predicts mortality (10), stroke (11), and the development of disability (12) in older adults.
Two sets of mechanisms could theoretically mediate the relationship between affective states and physical health. First, positive well-being might be associated with favorable health habits and prudent lifestyles. For example, cigarette smoking is associated with psychological distress (13), and depression and anxiety are inversely related to leisure-time physical activity (14). The second possibility is that associations are mediated through psychobiological processes, defined as the pathways by which psychosocial factors stimulate biological systems through central nervous system activation of autonomic, neuroendocrine, inflammatory, and immune responses. Depressed mood has been linked with increased levels of C-reactive protein and inflammatory cytokines (15), prolonged norepinephrine responses to stress (16), and deficient immune responses after vaccination (17).
The biological correlates of positive affective states are only beginning to be described. Positive affect is associated with greater degrees of left compared with right superior frontal EEG activity at rest (18). Tugade and Fridrickson (19) demonstrated that the rate of cardiovascular recovery after stress is more rapid in individuals expressing positive emotionality. Lindfors and Lundberg (20) reported a small study involving 23 individuals in which salivary cortisol sampled every 2 h over the working day was inversely related to scores on eudaimonic psychological well-being scales. No associations were observed with urinary catecholamines or blood pressure. Psychological well-being ratings have also been positively associated with cytokine production after vaccination for influenza and hepatitis (21).
We assessed the biological correlates of positive affective states both in everyday life settings and under standardized stress testing conditions. We were interested in health-related biological indicators, so we measured cortisol during the day, ambulatory blood pressure and heart rate, and plasma fibrinogen responses to challenging behavioral tasks. Most research on affective states relies on global evaluations of positive or negative affect taken on a single occasion. The limitations of such measures for estimating subjective experience include recall bias, memory distortion, and the dominant influence of current state (22). A preferable method is momentary experience sampling, in which participants are prompted to record what they are currently feeling on several occasions for one or more days. We aggregated momentary ratings of happiness sampled repeatedly over the working day to derive a more robust estimate of positive affect than might be generated on a single occasion. We hypothesized that positive affect would be inversely associated with cortisol, ambulatory blood pressure, and heart rate, and with reduced fibrinogen stress responsiveness, independently of other factors known to influence these biological variables. A second aim of this analysis was to discover whether associations between happiness and biological responses were independent of psychological distress. Participants completed the General Health Questionnaire (GHQ), a well established screening instrument for psychiatric disorders that measures psychological distress (23), that has been found to predict coronary heart disease prospectively (24). We expected GHQ scores to be negatively associated with happiness ratings and reasoned that if positive affective states are independently related to health-related biological factors, then effects should persist after statistical control for psychological distress.