Why Mortgage Sicken Us? 为什么房贷会让我们生病？
Glucocorticoids [1] plus the sympathetic nervous system [2] enables an organism to survive a physical stressor by activating the classical “fight or flight” response. The stress response rapidly mobilizes energy into circulation from storage sites in your body. Furthermore, heart rate and blood pressure increase, delivering that circulating energy to exercising muscles faster. Moreover, during stress, long-term building projects—growth, tissue repair, and reproduction—are postponed until after the crisis; Beta-endorphin is secreted, the immune system is stimulated, and blood clotting is enhanced, all useful following painful injury. Moreover, glucocorticoids reach the brain, rapidly enhancing aspects of cognition and sensory acuity.
Mobilizing energy while sprinting for your life helps save you. Do the same thing chronically because of a stressful twenty-year academic study and thirty-year housing mortgage, and you’re at risk for various metabolic problems, including adult-onset diabetes. Likewise with blood pressure: increase it to sprint across the savanna—good thing. Increase it because of chronic psychological stress, and you’ve got stress-induced hypertension. Chronically impair growth and tissue repair, and you’ll pay the price. Ditto for chronically inhibiting reproductive physiology; you’ll disrupt ovulatory cycles in women and cause plummeting erections and testosterone levels in men. Finally, while the acute stress response involves enhanced immunity, chronic stress suppresses immunity, increasing vulnerability to some infectious diseases.
The suppression of immunity and inflammation during chronic stress is caused by glucocorticoids. This is the reason why glucocorticoids are used to suppress the immune system in people with an overactive immune system (i.e., an autoimmune disease), to prevent rejection of a transplanted organ, or to suppress an overactive inflammatory response. This is what happens when people are put on immunosuppressive/anti-inflammatory “steroids” like cortisone or prednisone (two synthetic glucocorticoids).
It is rare for one to sicken because they can’t activate the stress response when it is needed. Instead, we get sick from activating the stress response too often, too long, and for purely psychological reasons. Crucially, the beneficial effects of the stress response play out over the course of seconds to minutes. But once you take stress to the time course of this article and thirty-year housing loan term (henceforth referred to as “sustained” stress), you’ll be dealing with adverse consequences.
If you’re stressed in an acute physical crisis, the stress response is lifesaving. But if instead you chronically activate the stress response for reasons of psychological stress, your health suffers.
There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
On such a full sea are we now afloat.
—William Shakespeare, Julius Caesar, act 4, scene 3
Annotations:
1. Critical events in the brain mediate the start of the stress response and activates the amygdala. The amygdala mediates main branch of the stress response, activating the paraventricular nucleus (PVN) in the hypothalamus. And the PVN sends projections to the base of the hypothalamus, where it secretes corticotropinreleasing hormone (CRH); this triggers the pituitary to release adrenocorticotropic hormone (ACTH), which stimulates glucocorticoid secretion from the adrenals.
2. The amygdala also mediates the other main branch of the stress response, activated amygdaloid neurons stimulate brain-stem neurons, which then inhibit the parasympathetic nervous system and mobilize the sympathetic nervous system, releasing epinephrine and norepinephrine throughout the body.
人生在世难免经历跌宕起伏，
也许踏浪前行即可功成名就；
倘若错失良机那么生命之旅
将淹没在苍茫无尽的痛苦中。
我们现在只能在苦海中漂浮。
——威廉·莎士比亚《恺撒大帝》第四幕第三场
为什么房贷会让我们生病？
糖皮质激素[1]加上交感神经系统[2]可以活化经典的“战或逃”反应，使有机体得以撑过生理上的压力。压力反应迅速动员能量从存储能量的地方进入身体循环—-你的心跳加快、血压身高、将循环中的能量送到肌肉，加速肌肉活动，要么打，要么逃。在面临压力时，体内长期工程—-生长、组织修复、生殖—-都暂缓，直到危机解除才会恢复正常运作。
为了保命而全速冲刺时，动员身体全部能量或战或逃可以救你一命，但如果背负20年的学业和30年的房屋贷款压力，长期动用全身能量，你就很有可能面临各种新陈代谢问题，如成人糖尿病；为了快速奔跑，血压上升事件好事，但是血压因为长期心理压力而上升，你就会得到压力引发的高血压；生长、生殖功能和组织修复长期受到抑制，最终也得付出代价，女性排卵期紊乱，男性勃起功能障碍和睾固酮下降。急性压力反应可以增进免疫力，但是长期慢性压力却会抑制免疫系统，身体更容易得到传染性疾病。
慢性压力期间，对免疫系统和发炎反应的抑制来自糖皮质激素，这就是为什么糖皮质激素会用来治疗免疫系统过度敏感、自体免疫疾病、避免器官移植的排斥反应，或者抑制过度激活的发炎反应。服用抑制免疫或消炎的类固醇如皮质醇cortisone（可的松）或泼尼松prednisone，这些合成的糖皮质激素corticosteroids的运作机制正是如此。
人类很少因为无法在需要时启动应激反应而生病。然而，我们却因为纯粹出于心理因素，太频繁又太长时间的启动应激反应而生病。如果我们能够在几秒钟到几分钟之间结束这个有意义的压力反应，可以提升我们的免疫力；不过，一旦你承受压力的时间长度接近阅读这篇文章的时间甚至是30年的房屋贷款期，那么这就成为一个持续的压力，你就被长期浸润在糖皮质激素中了，就会产生反效果。
如果你面临急性的生理危机，应激反应可以救你一命：如果你面临慢性生理压力而长期启动压力反应，就会对健康造成伤害。什么变压力为动力，化危机为转机，都是鸡汤，除非你的皮质激素能够拿得起还要能迅速放得下。
注释：
1. 应激反应 stress response就是一连串的神经和内分秘的变化，目的是帮助个体度过危机，并重建恒定状态。应激反应会活化杏仁核，杏仁核会调节一个主要的压力反应分支路径，活化下视丘的旁视核，旁视核反射到下视丘底部，那里会分泌促肾上腺皮质素释放激素(CRH)，这里会触发脑下垂体分泌促肾上腺皮质激素ACTH， ACTH会刺激肾上腺分泌糖皮质激素。
2. 应激反应会活化杏仁核，杏仁核也会调节另一个主要的压力反应分支路径，杏仁核神经元刺激脑干神经元，脑干接着抑制副交感神经系统，并启动交感神经系统，于是释放出肾上腺素和去甲肾上腺素到全身。
