研究称亲近大自然有助于改善情绪

A walk in the park may soothe the mind and, in the process, change the workings of our brains in ways that improve our mental health, according to an interesting new study of the physical effects on the brain of visiting nature.

根据一项以亲近自然对大脑的生理影响为主题的有趣的新研究，去公园散步或许能放松心神，在此期间让大脑的运作发生有助于改善精神健康状况的变化。

Most of us today live in cities and spend far less time outside in green, natural spaces than people did several generations ago.

如今，我们大多数人都生活在城市中，比起几代以前的人，我们与绿意盎然的自然空间相处的时间大大减少了。

City dwellers also have a higher risk for anxiety, depression and other mental illnesses than people living outside urban centers, studies show.

还有研究显示，城市居民感到焦虑、抑郁或出现其他精神问题的风险，高于居住在城市中心以外的人。

These developments seem to be linked to some extent, according to a growing body of research. Various studies have found that urban dwellers with little access to green spaces have a higher incidence of psychological problems than people living near parks and that city dwellers who visit natural environments have lower levels of stress hormones immediately afterward than people who have not recently been outside.

越来越多的研究表明，这些新情况之间似乎存在某种程度的关联。根据多项研究，基本不接触绿地的城市居民遭遇心理问题的几率，比住在公园附近的人要高;而城市居民在亲近大自然之后，体内压力荷尔蒙的水平立即就会低于近来没走出过家门的人。

But just how a visit to a park or other green space might alter mood has been unclear. Does experiencing nature actually change our brains in some way that affects our emotional health?

但目前还不清楚，逛公园或探访其他绿色空间可能如何改变人的情绪。亲近自然真能给我们的大脑带来某种会影响精神健康的改变吗?

That possibility intrigued Gregory Bratman, a graduate student at the Emmett Interdisciplinary Program in Environment and Resources at Stanford University, who has been studying the psychological effects of urban living. In an earlier study published last month, he and his colleagues found that volunteers who walked briefly through a lush, green portion of the Stanford campus were more attentive and happier afterward than volunteers who strolled for the same amount of time near heavy traffic.

这种可能性激起了斯坦福大学(Stanford University)埃米特环境与资源跨学科项目(Emmett Interdisciplinary Program in Environment and Resources)研究生格雷戈里·布拉特曼(Gregory Bratman)的兴趣，他一直在研究城市生活对心理的影响。在早前的一项研究中，他和同事们发现，志愿者短暂穿行于斯坦福校园内一片郁郁葱葱的绿地之中后，比那些花同样长的时间在交通繁忙处散了步的志愿者更专注，也更快乐，相关研究结果已于上月发表。

But that study did not examine the neurological mechanisms that might underlie the effects of being outside in nature. 但该研究并未考察或许在外出亲近自然的影响背后发挥作用的神经机制。

So for the new study, which was published last week in Proceedings of the National Academy of Sciences, Mr. Bratman and his collaborators decided to closely scrutinize what effect a walk might have on a person’s tendency to brood.

因此，布拉特曼及其同事决定在新研究中密切审视散步会对一个人沉溺于忧思的倾向产生什么影响，其研究成果于上周发表在了《国家科学院院刊》(Proceedings of the National Academy of Sciences)上。

Brooding, which is known among cognitive scientists as morbid rumination, is a mental state familiar to most of us, in which we can’t seem to stop chewing over the ways in which things are wrong with ourselves and our lives. This broken-record fretting is not healthy or helpful. It can be a precursor to depression and is disproportionately common among city dwellers compared with people living outside urban areas, studies show.

沉溺于忧思被认知科学家称为病态的反刍思考，是我们大多数人都很熟悉的一种心理状态，当我们陷入其中时，会情不自禁地反复琢磨我们自己以及我们的生活怎么就出了问题。这种过分的焦躁是不健康的，也于事无补。有研究显示，它可能是抑郁的先兆;比起住在城市地区以外的人，城市居民出现这种情况的比例奇高。

Perhaps most interesting for the purposes of Mr. Bratman and his colleagues, however, such rumination also is strongly associated with increased activity in a portion of the brain known as the subgenual prefrontal cortex.

不过，就布拉特曼及其同事的目的而言，最有趣的或许是：这种反刍思考与脑内膝下区前额叶皮层活动增加之间有很高的关联度。

If the researchers could track activity in that part of the brain before and after people visited nature, Mr. Bratman realized, they would have a better idea about whether and to what extent nature changes people’s minds.

布拉特曼意识到，如果研究人员能在人们亲近自然之前和之后追踪其脑内这一区域的活动，就可以更好地了解自然能否改变，或者能在多大程度上改变人类的情绪。

Mr. Bratman and his colleagues first gathered 38 healthy, adult city dwellers and asked them to complete a questionnaire to determine their normal level of morbid rumination.

布拉特曼及其同事先是找到38名健康且已成年的城市居民，并让他们完成一份问卷，以确定通常情况下他们的病态反刍思考指数。

The researchers also checked for brain activity in each volunteer’s subgenual prefrontal cortex, using scans that track blood flow through the brain. Greater blood flow to parts of the brain usually signals more activity in those areas.

研究人员还通过以扫描仪追踪每名志愿者脑部的血流，检查了其膝下区前额叶皮层的活动。通常而言，脑部哪个区域的血流量增大，就代表着那个区域的活动增多。

Then the scientists randomly assigned half of the volunteers to walk for 90 minutes through a leafy, quiet, parklike portion of the Stanford campus or next to a loud, hectic, multi-lane highway in Palo Alto. The volunteers were not allowed to have companions or listen to music. They were allowed to walk at their own pace.

随后，科学家们随机分派半数志愿者在斯坦福校园内一个绿荫环绕、安安静静，仿佛公园般的去处散步90分钟，另外半数则被分派到帕罗奥图的一条嘈杂、繁忙的多车道高速公路边，走了同样长的时间。志愿者不得结伴而行或听音乐，但可以自行控制速度。

Immediately after completing their walks, the volunteers returned to the lab and repeated both the questionnaire and the brain scan.

散步一结束，志愿者便返回实验室，再一次填写问卷、做脑部扫描。

As might have been expected, walking along the highway had not soothed people’s minds. Blood flow to their subgenual prefrontal cortex was still high and their broodiness scores were unchanged.

不出所料，在高速公路边散步没有对人们的情绪起到抚慰作用。膝下区前额叶皮层的血流量仍然很高，他们的忧思指数也没变。

But the volunteers who had strolled along the quiet, tree-lined paths showed slight but meaningful improvements in their mental health, according to their scores on the questionnaire. They were not dwelling on the negative aspects of their lives as much as they had been before the walk.

但问卷上的分数显示，那些沿着绿树成荫的静谧小路散步的志愿者，精神健康状况出现了虽然不大但却很有意义的改善。他们对生活的消极面的关注程度比出去散步前要低。

They also had less blood flow to the subgenual prefrontal cortex. That portion of their brains were quieter.

膝下区前额叶皮层的血流量也下降了。他们脑部的那一区域更为平静。

These results “strongly suggest that getting out into natural environments” could be an easy and almost immediate way to improve moods for city dwellers, Mr. Bratman said.

布拉特曼说，这些结果“强烈暗示，外出亲近大自然”是改善城市居民情绪的一个简单而又近乎立竿见影的方法。