摘要：Objectives. We sought to test the hypothesis that providing help to others predicts a reduced association between stress and mortality. Methods. We examined data from participants (n = 846) in a study in the Detroit, Michigan, area. Participants completed baseline interviews that assessed past-year stressful events and whether the participant had provided tangible assistance to friends or family members. Participant mortality and time to death was monitored for 5 years by way of newspaper obituaries and monthly state death-record tapes. Results. When we adjusted for age, baseline health and functioning, and key psychosocial variables, Cox proportional hazard models for mortality revealed a significant interaction between helping behavior and stressful events (hazard ratio [HR] = 0.58; P < .05; 95% confidence interval [CI] = 0.35, 0.98). Specifically, stress did not predict mortality risk among individuals who provided help to others in the past year (HR = 0.96; 95% CI = 0.79, 1.18), but stress did predict mortality among those who did not provide help to others (HR = 1.30; P < .05; 95% CI = 1.05, 1.62). Conclusions. Helping others predicted reduced mortality specifically by buffering the association between stress and mortality. In a seminal review published more than 20 years ago, House et al. described the strong association between social connections and physical health. 1 The researchers concluded that socially isolated people, compared with those with strong social ties, were at substantially increased risk of mortality and morbidity. In fact, the magnitude of the association between social isolation and mortality was comparable to that for high blood pressure, smoking, and sedentary lifestyle, even after statistical controls for other known risk factors such as baseline health. Despite the robustness of this effect, it remains unclear what aspects of the social environment influence physical health outcomes. One hypothesized link between social connections and health is that the social support people receive from their network of friends and loved ones may “buffer” against the detrimental physical consequences of psychosocial stress. 2,3 Indeed, stressful life events have long been established to be a predictor of increased mortality risk. 4,5 However, the social support hypothesis has not been consistently supported in empirical studies. Although some empirical studies suggest health benefits of received social support—and at least 1 indicates that these benefits accrue via stress buffering 6 —a meta-analytic review concluded that the overall relationship between receiving support and health outcomes “may not be considered significant or generalizable.”7(p352) This may be why House, in 2001, concluded that after nearly 2 decades of empirical work, very little is known about how social connectivity, as opposed to isolation, translates into physical health outcomes. 8 The failure of the social support hypothesis to account for the links between social connectedness and health 8 has prompted research on whether health may be associated with the other side of social interactions—namely, the provision of help and support to others. Providing help to others appears to promote the helper’s health, even when there is statistical control for plausible confounds such as baseline physical health and functioning or receiving support from others. For example, volunteering predicts increased self-rated health and longevity. 9–13 In a similar way, providing aid to a relationship partner predicts reduced morbidity and mortality. 14–16 Given the robust associations between support provision and health, it is possible that support provision may have stress-buffering effects even if the receipt of support does not. To date, health research has not explicitly tested this hypothesis; however, providing help to others has psychological and physiological correlates that may buffer against stress. For example, helping leads to improved mood, 17,18 which itself may act as a stress buffer. 19 In addition, caring for loved ones, in particular, may draw on the functioning of neural and hormonal mechanisms that support parenting behavior 20–22 —that is, the caregiving behavioral system. 23,24 Several hormones and neurochemicals associated with the caregiving system, including oxytocin, prolactin, and endogenous opioids, have known stress-reducing effects. 20,25–29 Laboratory and field studies provide preliminary evidence consistent with the prediction that providing help or support may act as a physiological stress buffer. Communicating affection to a relationship partner has been shown to predict reduced perceived stress, lowered baseline cortisol levels, 30,31 and faster recovery from peak cortisol levels following lab stressors. 32 In a similar way, experimentally manipulated helping predicts reduced cardiovascular reactivity to and faster cardiovascular recovery from laboratory stressors (written communication from Stephanie L. Brown, October 3, 2008). In addition, field studies indicate that engaging in helping behavior may buffer the effects of stress-related constructs on health-related outcomes. For example, engaging in helping behavior versus not doing so predicts lessened associations between grief and subsequent depression, 33 financial difficulties and mortality, 34 and functional limitations and mortality. 35 Research to date has not specifically examined whether providing help or support to others can buffer the associations between psychosocial stress and physical health outcomes. We sought to do so by using survey data from the Changing Lives of Older Couples (CLOC) study. The CLOC data set included 5-year survival data on a sample of 846 older adults along with baseline measures of helping, past-year stressful events, and potential confounds (e.g., demographic and socioeconomic factors, baseline health and well-being, personality, and social support receipt), allowing for a test of the stress-buffering role of prosocial behavior. We hypothesized that exposure to a recent stressful life event would moderate the association between helping behavior and mortality and vice versa. That is, we predicted that helping behavior would most strongly predict reduced mortality among individuals exposed to significant stress compared with those not exposed.
