Though most of us spend a lifetime pursuing happiness, new research is showing that that goal may be largely out of our control. Two new studies this month add to a growing body of evidence that factors like genes and age may impact our general well-being more than our best day-to-day attempts at joy.

In one study, researchers at the University of Edinburgh suggest that genes account for about 50% of the variation in people's levels of happiness - the underlying determinant being genetically determined personality traits, like "being sociable, active, stable, hardworking and conscientious," says co-author Timothy Bates. What's more, says Bates, these happiness traits generally come as a package, so that if you have one you're likely to have them all.

Bates and his Edinburgh colleagues drew their conclusions after looking at survey data of 973 pairs of adult twins. They found that, on average, a pair of identical twins shared more personality traits than a pair of non-identical twins. And when asked how happy they were, the identical twin pairs responded much more similarly than other twins, suggesting that both happiness and personality have a strong genetic component. The study, published in Psychological Science, went one step further: it suggested that personality and happiness do not merely coexist, but that in fact innate personality traits cause happiness. Twins who had similar scores in key traits - extroversion, calmness and conscientiousness, for example - had similar happiness scores; once those traits were accounted for, however, the similarity in twins' happiness scores disappeared.

Another larger study, released in January ahead of its publication in Social Science & Medicine this month, shows that whatever people's individual happiness levels, we all tend to fall into a larger, cross-cultural and global pattern of joy. According to survey data representing 2 million people in more than 70 countries, happiness typically follows a U-shaped curve: among people in their mid-40s and younger, happiness trends downward with age, then climbs back up among older people. （That shift doesn't necessarily hold for the very old with severe health problems.） Across the world, people in their 40s generally claim to be less happy than those who are younger or older, and the global happiness nadir appears to hit somewhere around 44.

What happens at 44? Lots of things, but none that can be pinned down as the root cause of unhappiness. It's not anxiety from the kids, for starters. Even among the childless, those in midlife reported lower life satisfaction than the young or old, says study co-author Andrew Oswald, an economics professor at the University of Warwick in Britain. Other things that didn't alter the happiness curve: income, marital status or education. "You can adjust for 100 things and it doesn't go away," Oswald says. He and co-author David Blanchflower, an economist at Dartmouth College in New Hampshire, also adjusted their results for cohort effects: their data spanned more than 30 years, making them confident that whatever makes people miserable about being middle-aged, it isn't related, say, to being born in the year 1960 and growing up with that generation's particular set of experiences.

At first glance, the new studies may appear at odds with some previous ones, largely because in happiness research, a lot depends on how you ask the question. Oswald and Blanchflower looked at responses to a sweeping, general question: "Taken all together, how would you say things are these days - would you say that you are very happy, pretty happy or not too happy?" （The wording changes slightly depending on where the survey was conducted, but the question is essentially the same.） In a 2001 study, Susan Charles at University of California, Irvine, measured something slightly different: changes in positive affect, or positive emotions, versus negative affect over more than 25 years. Charles found that positive affect stayed roughly stable through young adulthood and midlife, falling off a little in older age; negative affect, meanwhile, fell consistently with age.

Charles thinks that feelings like angst, disgust and anger may fade because as we get older we learn to care less about what others think of us, or perhaps because we become more adept at avoiding situations we don't like. （The Edinburgh researchers, too, found that older study participants scored lower than younger ones on scales of neuroticism - worry and nervousness - and higher on scales of agreeableness.） Oswald chalks up the midlife dip in happiness shown in his study to people "letting go of impossible aspirations" - first, there's the pain of fading youth and the realization that we may never accomplish all that we had dreamed, then the contentment we gain later in life through acceptance and self-awareness. "When you're young you can't do that," Oswald says.

An oft-cited finding from other happiness research suggests, however, that neither very good events nor very bad events seem to change people's happiness much in the long term. Most people, it seems, revert back to some kind of baseline happiness level within a couple years of even the most devastating events, like the death of a spouse or loss of limbs. Perhaps that kind of stability is due to heredity - those happiness-inducing personality traits that identical twins have been shown to share.

Still, lack of control doesn't necessarily mean lack of joy. "The research also shows that most people consider themselves happy most of the time," says University of Edinburgh's Bates. "We're wired to be optimistic. Most people think they're happier than most [other] people." And even if you aren't part of that lucky majority, Bates says, there's always that other 50% of overall life satisfaction that, according to his research, is not genetically predetermined. To feel happier, he recommends mimicking the personality traits of those who are: Be social, even if it's only with a few people; set achievable goals and work toward them; and concentrate on putting setbacks and worries in perspective. Don't worry, as the saying goes. Be happy.

虽然我们大多数人用一生来追寻幸福，但最新研究表明，这个目标很大程度上不受我们控制。本月公布的两个新研究又一次证明，基因、年龄等因素对幸福感的影响，可能比我们每天作出的努力来得更加显着。

爱丁堡大学的研究者认为，基因决定着大约50%的人类幸福程度变量--这正是形成坚强性格特征的潜在决定因素，合作研究者Timothy Bates说，这些特征包括"社交活跃、积极、稳定、勤奋和尽责".他还表示，这些幸福的特质通常同时体现出来，因此如果你具备其中一个，则很可能也拥有全部特征。

Bates和他的同事调查了973对成年双胞胎后得出了这些结论。他们发现，一般来说，相比起非同卵的双胞胎，一卵双生的双胞胎在性格上具有更多相同点。当被问到他们感觉有多快乐，一卵双生双胞胎的回答相似度比其他双胞胎要高得多，这显示出幸福感和性格有着强烈的基因成分。这个刊登在《心理科学》杂志上的研究进一步表明：性格和幸福感并非单纯的共存关系，实际上正是天生的性格特质带来了幸福感。在关键特征上--比如外向、平和、尽责等，拥有相似分数的双胞胎，其幸福感指数也很相近；然而，一旦这些特质的分数不同，幸福感指数也随之不尽相同。

另一项大型研究结果在一月份发表，并于本月刊登在《社会科学和医学》上。它显示，无论人们个人的幸福感水平如何，我们都落入了一个更宏大的、跨文化的、全球性的快乐模式中。根据对超过70个国家，两百万人的调查，幸福感呈现出典型的U型曲线：在四十多岁的人群中，幸福感随着年龄的增长而下降，然后在更年长的人群中又有所回升（这不包括那些遭受严重健康问题的人）.全世界范围内，四十多岁的人群一般都比更年轻或更年长的人感到更少快乐，幸福低谷出现在大约44岁的年龄段。

44岁发生了什么？许多事情，但没有一样能够被视为不幸福的根源。研究者起先以为是来自对子女的忧虑，但不是。合作研究者，来自英国华威大学的经济学教授Andrew Oswald表示，即使在没有子女的中年人中，他们同样比更年轻和更年长的人感受到更低的生活满意度。其它事物，诸如收入、婚姻状态和教育等均无法改变幸福曲线的走向。Oswald说："你可以调整100样事情，但它就是不变。"他和另一位合作研究者，新汉普郡达特茅斯学院的经济学家David Blanchflower, 因应"群效应"而调整了研究：他们的研究数据延续超过30年，使他们确信，无论是什么因素使人们在中年阶段感到不快乐，都与其所处的特定时代无关，例如都出生在1960年并具有那一代人的独特经历。

乍看起来，这些新研究与之前的很不一致，这大部分是因为在幸福感研究中，如何设问是很关键的。Oswald和Blanchflower提出的是一个宏观的、全面性的"大问题":"总的来说，你怎么描述这些年来的各种事情？--你会说非常快乐、相当快乐还是不怎么快乐？"（用词随着调查地点的转变有些许变化，但问题基本上是一样的。）在2001年，加州大学尔湾分校的Susan Charles在研究中使用了稍不同的尺度：在超过25年里，积极的影响、积极的情绪的变化与消极的影响的对比。Charles发现积极的影响在青年和中年时代大致保持稳定，在更年长时稍微下跌；同时，消极影响随着年龄持续地下降。

Charles认为，像悲伤、厌恶和愤怒等情感逐渐减弱，是因为随着年龄渐长，我们学会了不再那么在意别人的眼光，或者是因为我们更能够审时度势，避开不利的局面。（爱丁堡的研究者同样发现，年长的调查对象在神经过敏程度上，如忧虑、紧张等，比年轻者分数较低；而在合作宽容程度上得分较高）.Oswald认为，研究显示的中年幸福低谷是因为人们"不得不放弃无法实现的梦想".首先，人们需要面对青春消逝的无奈，并意识到自己可能永远不能实现所有的梦想了。然后，当更年长一些之后，人们又通过宽容和自我觉醒获得了满足感。"当你年轻的时候你做不到这样。" Oswald说。

一个经常被引用的幸福感研究结果表明，极好和极坏的事件似乎并不能明显改变人们在长期内的幸福感水平。多数人经历过最惨痛的事情，例如配偶死亡或肢体残疾等，之后的若干年内，他们的幸福感水平又回复到某个基线上。也许这种稳定性来自于遗传--即那些能够促进幸福感的性格特质，正如一卵双生双胞胎表现出来的那样。

当然，无法控制幸福感水平并不意味着失去欢乐。"研究同时显示，多数人认为他们大多数时候都是快乐的。"爱丁堡大学的Bates说，"我们倾向于乐观。多数受访者认为他们比大多数其他人更快乐。"即使你不是那幸运的大多数，Bates说，根据他的研究，仍然有另外50%的生活满意度并非由基因注定。要感受快乐，他建议仿效快乐者的性格特质：积极社交，即使只是和一些人；设定可达成的目标并努力去实现；注意消除自己观念里的忧虑和挫折感。别担心，正如俗语说的。快乐吧！