总结一下：
作者研究平均年龄大约60岁的女性，让她们自我评估“快乐”感。然后比较十年后的死亡率。首先，70岁低于英国女性的预期年龄，所以这期间只有4%的人死亡。更重要的是，作者的结论并不是直接比较死亡率，而是用数据处理的方法去除了很多因素，包括研究开始时的自我健康评估，高血压，糖尿病，哮喘，关节炎，抑郁症，焦虑症等。最后得出的结论是这么处理完的数据显示死亡率和一开始的快乐评估无关。
作者认为去除这些因素是合理的，因为它们不是不快乐的结果，而是不快乐的原因。
总之，结论就是，如果把跟死亡率相关的因素都去除的话，死亡率就是相同的。什么叫“按摩数据”，这就叫按摩数据！
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(15)01087-9/abstract
Does happiness itself directly affect mortality? The prospective UK Million Women Study
Summary
Background
Poor health can cause unhappiness and poor health increases mortality. Previous reports of reduced mortality associated with happiness could be due to the increased mortality of people who are unhappy because of their poor health. Also, unhappiness might be associated with lifestyle factors that can affect mortality. We aimed to establish whether, after allowing for the poor health and lifestyle of people who are unhappy, any robust evidence remains that happiness or related subjective measures of wellbeing directly reduce mortality.
Methods
The Million Women Study is a prospective study of UK women recruited between 1996 and 2001 and followed electronically for cause-specific mortality. 3 years after recruitment, the baseline questionnaire for the present report asked women to self-rate their health, happiness, stress, feelings of control, and whether they felt relaxed. The main analyses were of mortality before Jan 1, 2012, from all causes, from ischaemic heart disease, and from cancer in women who did not have heart disease, stroke, chronic obstructive lung disease, or cancer at the time they answered this baseline questionnaire. We used Cox regression, adjusted for baseline self-rated health and lifestyle factors, to calculate mortality rate ratios (RRs) comparing mortality in women who reported being unhappy (ie, happy sometimes, rarely, or never) with those who reported being happy most of the time.
Findings
Of 719?671 women in the main analyses (median age 59 years [IQR 55–63]), 39% (282?619) reported being happy most of the time, 44% (315?874) usually happy, and 17% (121?178) unhappy. During 10 years (SD 2) follow-up, 4% (31?531) of participants died. Self-rated poor health at baseline was strongly associated with unhappiness. But after adjustment for self-rated health, treatment for hypertension, diabetes, asthma, arthritis, depression, or anxiety, and several sociodemographic and lifestyle factors (including smoking, deprivation, and body-mass index), unhappiness was not associated with mortality from all causes (adjusted RR for unhappy vs happy most of the time 0·98, 95% CI 0·94–1·01), from ischaemic heart disease (0·97, 0·87–1·10), or from cancer (0·98, 0·93–1·02). Findings were similarly null for related measures such as stress or lack of control.
Interpretation
In middle-aged women, poor health can cause unhappiness. After allowing for this association and adjusting for potential confounders, happiness and related measures of wellbeing do not appear to have any direct effect on mortality.
Funding
UK Medical Research Council, Cancer Research UK.
