When is stress good for you?
Bruce McEwen
The subtle flows and toxic hits of stress get under the skin, making and breaking the body and brain over a lifetime
压力的微妙涌动和有毒攻击钻进了皮肤,终身改变和破坏着身体和大脑。
Stress pervades our lives. We become anxious when we hear of violence, chaos or discord. And, in our relatively secure world, the pace of life and its demands often lead us to feel that there is too much to do in too little time. This disrupts our natural biological rhythms and encourages unhealthy behaviours, such as eating too much of the wrong things, neglecting exercise and missing out on sleep.
焦虑不安。而且,这个相对安全的世界里的生活节奏和生活需求,常常使我们感到在有限的时间里有太多的事情要做。这扰乱了我们的自然生物节律,助长了不健康的行为,比如吃了太多错误的东西、忽视了锻炼、错过了睡眠。
压力弥散在我们的生活中,当我们听到暴力、混乱和不和时,就会变得Racial and ethnic discrimination, along with lack of educational opportunities and economic advancement take their toll on a large segment of the population in the United States. Incarceration is the rule rather than the exception for some of the most vulnerable. Adverse experiences in infancy and childhood, including poverty, leave a lifelong imprint on the brain and body, and undermine long-term health, increasing the incidence of cardiovascular disease, diabetes, depression, substance abuse, anti-social behaviour and dementia. How does all of this stress ‘get under our skin’? What does it do to our brains and our bodies? What can we do about it? And is stress so multifaceted and pervasive that we could have trouble controlling it at all?
种族和民族歧视,加上缺乏教育机会和经济发展机会,使很大一部分美国人口付出了代价。对于某些最弱的群体而言,监禁是规则而不是例外。包括贫穷在内的婴儿和儿童时期的不幸经历给大脑和身体留下终生印记,并损害长期健康,增加心血管疾病、糖尿病、抑郁症、药物滥用、反社会行为和痴呆的发生率。所有这些压力是如何“深入我们的皮肤”的?它对我们的大脑和身体有什么影响?我们能做什么?压力是如此的多方面和普遍性,以至于我们根本无法控制它们么?
The psychologist Jerome Kagan at Harvard University recently complained that the word ‘stress’ has been used in so many ways as to be almost meaningless; he suggests it’s warranted only for the most extreme circumstances or damaging events. But my decades of experience suggest another approach. The insidious power of stress to ‘get under the skin’ was the focus of a MacArthur Foundation Research Network that I joined more than two decades ago, uniting me with social scientists, physicians and epidemiologists around a common problem: how to measure and evaluate stress from our social and physical environments. Our collaboration, continued under the auspices of the National Scientific Council on the Developing Child, has shown that stress acts on the body and brain, profoundly influencing health and disease.
哈佛大学的心理学家杰罗姆·卡根(Jerome Kagan)最近抱怨说,“压力”一词已经被过度使用,几乎没有任何意义。他建议仅在最极端的情况下或有破坏性的事件中使用它。但是我数十年的经验提出了另一种方法。压力隐匿在皮肤下的强大力量是我二十多年前加入的麦克阿瑟基金会研究网络的重点,该网络将我与社会科学家,医师和流行病学家联合起来,围绕着一个常见问题:如何衡量和评估压力来自我们的社交和自然环境。在国家儿童发展科学委员会的主持下,我们的合作表明,压力作用于身体和大脑,深刻影响健康和疾病。
Our findings are nuanced, starting with the fact that not all stress is the same. ‘Good stress’ involves taking a chance on something one wants, like interviewing for a job or school, or giving a talk before strangers, and feeling rewarded when successful. ‘Tolerable stress’ means that something bad happens, like losing a job or a loved one, but we have the personal resources and support systems to weather the storm. ‘Toxic stress’ is what Kagan refers to – something so bad that we don’t have the personal resources or support systems to navigate it, something that could plunge us into mental or physical ill health and throw us for a loop.
我们发现十分微妙,事实是——并非所有压力都是相同。“良好的压力”能够让人们抓住机会得到自己想要的东西,例如面试工作或上学,或在陌生人面前演讲,并在成功时感到收获。“可承受的压力”意味着会发生一些不好的事情,例如失业或亲人失去工作,但我们拥有个人资源和支持系统,可以度过难关。Kagan所指的是“有毒的压力”,这很糟糕,以至于我们没有个人资源或支持系统来应对它,这可能会使我们陷入精神或身体疾病,并使我们陷入困境。
Now let us put these three forms of stress into a biological and behavioural context by invoking ‘homeostasis’ – the physiological state maintained by the body to keep us alive. It is through homeostasis that we maintain body temperature and pH (alkalinity and acidity) within a narrow range, keep our tissues perfused with oxygen and our cells fed. To maintain this steady state, our body secretes hormones such as adrenalin. Indeed, when we encounter an acute perceived threat – a large, menacing dog, for example – the hypothalamus, at the base of our brain, sets off an alarm system in our body, sending chemical signals to the pituitary gland. The pituitary, in turn, releases ACTH (Adrenocorticotropic hormone) that activates our adrenal glands, next to our kidneys, to release adrenalin and the primary stress hormone, cortisol. Adrenalin increases heart rate, blood pressure and energy supplies; cortisol increases glucose in the blood stream and has many beneficial effects on the immune system and brain, among other organs. In a fight-or-flight situation cortisol moderates immune-system responses, and suppresses the digestive system, the reproductive system and growth processes, as well as signalling brain regions that control cognitive function, mood, motivation and fear.
现在,让我们通过调用“内稳态(homeostasis)”将这三种压力形式置于生物学和行为环境中,“内稳态”是指人体维持生命的生理状态。通过内稳态,我们可以将体温和pH值(碱度和酸度)保持在一个狭窄的范围内,使我们的组织充满氧气,并使我们的细胞饱食。为了保持这种稳定状态,我们的身体会分泌激素,例如肾上腺素。确实,当我们遇到严重的感知威胁时(例如,一只大而凶险的狗),大脑底部的下丘脑在我们的身体内发出警报系统,向垂体发送化学信号。垂体又释放ACTH(促肾上腺皮质激素),该激素激活我们靠近肾脏的肾上腺,释放肾上腺素和主要的应激激素皮质醇。肾上腺素会增加心率,血压和能量供应;皮质醇增加血液中的葡萄糖,并对免疫系统和大脑以及其他器官产生许多有益作用。在战斗或逃跑情况下,皮质醇会调节免疫系统反应,并抑制消化系统,生殖系统和生长过程,并发出控制认知功能、情绪、动机和恐惧的大脑区域信号。
Biochemical mediators such as cortisol and adrenalin help us to adapt – as long as they are turned on in a balanced way when we need them, and then turned off again when the challenge is over. When that does not happen, these ‘hormones of stress’ can cause unhealthy changes in brain and body – for example, high or low blood pressure, or an accumulation of belly fat. When wear and tear on the body results from imbalance of the ‘mediators’, we use the term ‘allostatic load’. When wear and tear is strongest, we call it allostatic overload, and this is what occurs in toxic stress. An example is when bad health behaviours such as smoking, drinking and loneliness result in hypertension and belly fat, causing coronary artery blockade. In short, the mediators that help us to adapt and maintain our homeostasis to survive can also contribute to the well-known diseases of modern life.
孤独等不良健康行为导致高血压和腹部脂肪,导致冠状动脉阻塞。简而言之,
生化介质(例如皮质醇和肾上腺素)可以帮助我们适应——只要在需要时以平衡的方式打开它们,然后在挑战结束后再次关闭它们。如果这种情况没有发生,这些“压力荷尔蒙”可能会导致大脑和身体发生不健康的变化,例如,血压升高或降低或腹部脂肪堆积。当由于“调解人”的不平衡而导致身体磨损时,我们使用“非稳态负荷(allostatic load)”一词。当磨损最强时,我们称其为超过载(allostatic overload),这就是在有毒压力下发生的情况。例如,吸烟,饮酒和The word stress is often explained as a ‘fight-or-flight response’. But what really affects our health and wellbeing are the more subtle, gradual and long-term influences from our social and physical environment – our family and neighbourhood, the demands of a job, shift work and jet lag, sleeping badly, living in an ugly, noisy and polluted environment, being lonely, not getting enough physical activity, eating too much of the wrong foods, smoking, drinking too much alcohol. All these contribute to allostatic load and overload through the same biological mediators that help us to adapt and stay alive.
Even though we now know all this, we often hear that measuring our cortisol levels will tell us if we are stressed. This reflects a misunderstanding at two levels. First, a single measure of cortisol will tell us nothing since cortisol levels go up and down within minutes – and halting this fluctuation impairs ongoing adaptive plasticity within the brain. Moreover, cortisol fluctuates throughout the day, going up in the morning to awaken us and then declining, except for a rise at lunch time, until it falls to low levels in the evening before we go to bed. Flattening this diurnal rhythm is a consequence of sleep deprivation and certain forms of major depression; a flat rhythm not only attenuates a robust, adaptive cortisol stress response but it also promotes obesity and high cholesterol, risk factors for diabetes and cardiovascular disease. It does so in part by causing the liver to make the ingredients to deposit body fat.