（本文编译自纽约时代周刊 24/04/2019期，加了我自己许多知识和解释。英文原文附在下面）
和许多注重健康的人一样，你可能已经决定要少花点时间盯着手机看了。
这是个好主意：越来越多的证据表明，我们在我们的智能手机上耗费的时间正在干扰我们的睡眠、自信、人际关系、记忆、注意力、创造力、生产力以及解决问题和决策的能力。
但还有另一个重要原因使我们重新思考与这些电子设备的关系的。使用手机时，身体的应急激素-固醇类皮质激素会加大分泌，体内处于长期慢性的高皮质激素水平会威胁我们的健康，并缩短我们的寿命。
到目前为止，大多数关于手机生化效应的讨论都集中在多巴胺上，多巴胺是一种帮助我们形成习惯和上瘾的大脑化学物质，多巴胺会给我们愉悦感。它在体内的合成和释放是我们大脑为鼓励我们形成做某种事情的习惯而动用的生理机制。就像老虎机一样，智能手机和应用程序明显是为了触发多巴胺的释放而设计的，目的就是让我们难以放下手中的设备。
我们多巴胺系统对使用手机的生理反应，正是许多专家认为为什么我们会对手机上瘾的原因。但是现在我们体内的另一组激素：固醇类皮质激素受到手机的影响可能更令人担忧。
固醇类皮质激素是身体应激状况时(fight & flight)分泌的主要激素。它的释放会引发一些生理变化，比如血压、心率和血糖的飙升，呼吸加快，皮肤、泪腺变干，这些变化会帮助我们对紧急的人身威胁做出反应并存活下来。
如果你的身体确实存在危险，比如一头公牛正在向你冲来，这些反应将可以挽救你的生命。大都市的现代生活当然不太会有公牛，不过下面这些情况都属于应激状况，固醇类皮质激素都会或多或少地增加分泌：过马路，开车，运动，比赛，演讲；当然还有工作压力，财务压力，养育孩子的压力，婚姻关系人事关系的压力等等；还有情绪上的愤怒怨恨也是身体偏向应激，提高皮质激素分泌的状态。
对应应激状况而言，身体有另一个状态-休息和维修(rest & digest)。下面这些情况属于休息和维修状态：吃饭，睡觉，听轻柔音乐，欣赏美景，当然还有投入地做气功瑜伽时。
医学和科学证实，在使用手机时，身体是的偏向应激状态的，也就是说固醇类皮质激素分泌是偏高的。
一天4小时
如果这只是偶尔发生，手机引起的固醇类皮质激素激增可能并不重要。但据一款名为Moment的追踪应用显示，美国人平均每天要花四个小时盯着自己的智能手机，而且几乎时时刻刻都把它放在触手可及的地方。正如谷歌在一份报告中所指出，其结果是，“装有社交媒体、电子邮件和新闻应用的移动设备”会产生“一种持续的责任感，进而形成意想不到的个人压力。”
“当你的手机在你的视线范围内或附近，又或者当你听到它，甚至认为你听到它时，你的固醇类皮质激素水平就会升高。”康涅狄格大学(University of Connecticut)医学院的临床精神病学教授、互联网和科技成瘾研究中心(Center for Internet and Technology Addiction)的创始人大卫·格林菲尔德(David Greenfield)说。“这是一种压力反应，它让人感到不舒服，而身体的自然反应是想要看看手机，让这种压力消失。”
虽然这样做可能会让你暂时平静下来，但从长远来看，它可能会让事情变得更糟。每次你查看手机的时候，都很可能发现，一些随之而来的压力正在等着你，这会导致固醇类皮质激素再次飙升，并产生另一种想要查看手机让你的焦虑消失的渴望。如果这种循环不断加强，将导致固醇类皮质激素水平长期升高。
而固醇类皮质激素水平的长期慢性升高已被发现与多种严重健康问题的风险增加有关，包括焦虑、抑郁、肥胖、代谢综合征、乙型糖尿病、生育问题、高血压、心脏病、老年失智和中风。“我们所知的各种慢性病都会因压力而恶化，”加州大学教授罗伯特·拉斯蒂格(Robert Lustig)说。“而我们的手机无疑在加剧这一点。”
智能手机压力
除潜在的长期健康不良影响之外，智能手机引起的压力还可能直接威胁生命。固醇类皮质激素水平的升高会损伤大脑前额皮质，这一大脑区域对决策与理性思考至关重要。如神经专家所言前，前额皮质能”让我们避免做蠢事。”
前额皮质受损会导致自我控制力降低。伴随着减轻焦虑的强烈欲望，会使我们做一些当前或许能暂时减缓压力，却有致命隐患的事情，比如边开车边发信息。如果我们时常都在担心什么坏事就要发生，压力的影响可能会被放大，无论是身体受攻击还是社交媒体上惹人不快的评论。（这种过度警觉有时表现为“幻觉震动”，即人们感觉手机在口袋里震动，而其实口袋里根本没有手机。）
“我们所做的每件事，所经历的每件事，都会对我们的生理机能产生影响，并改变我们的脑回路，使我们对压力的反应程度增强或减弱，美国科学家指出，在规律的24小时周期中，我们的基础固醇类皮质激素水平上下起伏，如果夜间睡眠不足7至8小时，这一运行节奏可能会陷入混乱，而如果有睡前查看手机的习惯，这种情况极易发生。这到头来导致身体对压力的恢复能力减弱，增加患上述所有压力相关健康状况的风险。
综合来看，我们花许多时间不由自主地查看手机，最终可能远不只是浪费了时间，对健康的影响才是巨大的忧虑。
打破这一循环
好消息是，如果我们将这一焦虑驱动的周期打破，便能降低固醇类皮质激素水平，进而有望改善短期判断能力，并降低患上长期压力相关健康问题的风险。久而久之，甚至有可能对大脑进行重新训练，使我们对压力的反应不再从一开始就进入一触即发的紧张状态。
为了让你的手机少制造些压力，可以从关闭所有消息通知开始，只留下你真正想接收的那些。接下来，留意一下你在使用不同应用时的感受。哪些是你出于焦虑查看的？哪些让你感到有压力？把这些应用隐藏到主屏幕之外的文件夹里。能把它们删掉几天时间看看感觉如何，那就更好了。
有规律的休息也是重新找回身体的化学平衡、重获控制感的有效方式。实行一次24小时的“数字安息日”可能会有意想不到的安抚功效，哪怕只是在午餐时把手机搁在一旁，也是朝正确的方向迈了一步。
此外，主动有意识地去体会要去看手机的欲望在大脑和身体里的感受是怎样的—不要立即顺应这些欲望。“如果你主动练习留意身体的内部感受，你会意识到你可以选择如何作出回应，”“我们没必要让自己被一些社交媒体上的长长短短所牵制。”
不走运的是，人们建立健康的习惯并不容易，毕竟这些电子设备是专门设计用来模糊这些习惯的。但通过降低我们的压力水平，为了健康建立我们和手机的界限将不仅会使我们一天天感觉好起来。它可能真的会延长我们的生活质量和生命。
Putting down Your Phone May Help You Live Longer
By raising levels of the stress-related hormone cortisol, our phone time may also be threatening our long-term health.
By Catherine Price
If you’re like many people, you may have decided that you want to spend less time staring at your phone.
It’s a good idea: an increasing body of evidence suggests that the time we spend on our smartphones is interfering with our sleep, self-esteem, relationships, memory, attention spans, creativity, productivity and problem-solving and decision-making skills.
But there is another reason for us to rethink our relationships with our devices. By chronically raising levels of cortisol, the body’s main stress hormone, our phones may be threatening our health and shortening our lives.
Until now, most discussions of phones’ biochemical effects have focused on dopamine, a brain chemical that helps us form habits — and addictions. Like slot machines, smartphones and apps are explicitly designed to trigger dopamine’s release, with the goal of making our devices difficult to put down.
This manipulation of our dopamine systems is why many experts believe that we are developing behavioral addictions to our phones. But our phones’ effects on cortisol are potentially even more alarming.
Cortisol is our primary fight-or-flight hormone. Its release triggers physiological changes, such as spikes in blood pressure, heart rate and blood sugar, that help us react to and survive acute physical threats.
These effects can be lifesaving if you are actually in physical danger — like, say, you’re being charged by a bull. But our bodies also release cortisol in response to emotional stressors where an increased heart rate isn’t going to do much good, such as checking your phone to find an angry email from your boss.
4 Hours a Day
If they happened only occasionally, phone-induced cortisol spikes might not matter. But the average American spends four hours a day staring at their smartphone and keeps it within arm’s reach nearly all the time, according to a tracking app called Moment. The result, as Google has noted in a report, is that “mobile devices loaded with social media, email and news apps” create “a constant sense of obligation, generating unintended personal stress.”
“Your cortisol levels are elevated when your phone is in sight or nearby, or when you hear it or even think you hear it,” says David Greenfield, professor of clinical psychiatry at the University of Connecticut School of Medicine and founder of the Center for Internet and Technology Addiction. “It’s a stress response, and it feels unpleasant, and the body’s natural response is to want to check the phone to make the stress go away.”
But while doing so might soothe you for a second, it probably will make things worse in the long run. Any time you check your phone, you’re likely to find something else stressful waiting for you, leading to another spike in cortisol and another craving to check your phone to make your anxiety go away. This cycle, when continuously reinforced, leads to chronically elevated cortisol levels.
And chronically elevated cortisol levels have been tied to an increased risk of serious health problems, including depression, obesity, metabolic syndrome, Type 2 diabetes, fertility issues, high blood pressure, heart attack, dementia and stroke.
“Every chronic disease we know of is exacerbated by stress,” says Dr. Robert Lustig, emeritus professor in pediatric endocrinology at the University of California, San Francisco, and author of “The Hacking of the American Mind.” “And our phones are absolutely contributing to this.”
Smartphone Stress
In addition to its potential long-term health consequences, smartphone-induced stress affects us in more immediately life-threatening ways.
Elevated cortisol levels impair the prefrontal cortex, an area of the brain critical for decision-making and rational thought. “The prefrontal cortex is the brain’s Jiminy Cricket,” says Dr. Lustig. “It keeps us from doing stupid things.”
Impairment of the prefrontal cortex decreases self-control. When coupled with a powerful desire to allay our anxiety, this can lead us to do things that may be stress-relieving in the moment but are potentially fatal, such as texting while driving.
The effects of stress can be amplified even further if we are constantly worrying that something bad is about to happen, whether it’s a physical attack or an infuriating comment on social media. (In the case of phones, this state of hypervigilance sometimes manifests as “phantom vibrations,” in which people feel their phone vibrating in their pocket when their phone isn’t even there.)
“Everything that we do, everything we experience, can influence our physiology and change circuits in our brain in ways that make us more or less reactive to stress,” says Bruce McEwen, head of the Harold and Margaret Milliken Hatch Laboratory of Neuroendocrinology at The Rockefeller University.
Dr. McEwen also notes that our baseline cortisol levels ebb and flow in a regular 24-hour cycle that is thrown out of whack if we get less than seven to eight hours of sleep a night, which is all too easy to do if you’re in the habit of checking your phone before bed. This in turn leaves our bodies less resilient to stress and increases our risk of all the stress-related health conditions mentioned above.
Put this all together, and the hours we spend compulsively checking our phones may add up to much more than a waste of time.
Breaking the Cycle
The good news is that if we break this anxiety-driven cycle, we can reduce our cortisol levels, which in turn may both improve our short-term judgment and lower our risks for long-term stress-related health problems. Over time, says Dr. McEwen, it’s even possible to retrain our brains so that our stress responses are no longer on such a hair-trigger to begin with.
To make your phone less stressful, start by turning off all notifications except for the ones you actually want to receive.
Next, pay attention to how individual apps make you feel when you use them. Which do you check out of anxiety? Which leave you feeling stressed? Hide these apps in a folder off your home screen. Or, better yet, delete them for a few days and see how it feels.
And while you’re at it, start paying attention to how individual apps affect you physically, too. “If we’re not aware of our physical sensations, we’re not going to change our behaviors,” says Dr. Judson Brewer, director of research and innovation at the Mindfulness Center at Brown University and author of “The Craving Mind.” According to Dr. Brewer, stress and anxiety often manifest as a feeling of contraction in the chest.
Regular breaks can also be an effective way to rebalance your body’s chemistry and regain your sense of control. A 24-hour “digital Sabbath” can be surprisingly soothing (once the initial twitchiness subsides), but even just leaving your phone behind when you get lunch is a step in the right direction.
Also, try to notice what anxiety-induced phone cravings feel like in your brain and body — without immediately giving in to them. “If you practice noticing what is happening inside yourself, you will realize that you can choose how to respond,” says Jack Kornfield, a Buddhist teacher at the Spirit Rock Meditation Center in California. “We don’t have to be at the mercy of algorithms that are promoting the fear of missing out.”
Unfortunately, it isn’t easy to create healthy boundaries with devices that are deliberately designed to discourage them. But by reducing our stress levels, doing so won’t just make us feel better day-to-day. It might actually lengthen our lives.
Catherine Price (@catherine_price) is the author of “How to Break Up With Your Phone” and creator of Screen/Life Balance.