Are you sleeping restlessly, feeling irritable or moody, forgetting little things, and feeling overwhelmed and isolated? Don't worry. We've all been there. You're probably just stressed out. Stress isn't always a bad thing. It can be handy for a burst of extra energy and focus, like when you're playing a competitive sport, or have to speak in public. But when its continuous, the kind most of us face day in and day out, it actually begins to change your brain. Chronic stress, like being overworked or having arguments at home, can affect brain size, its structure, and how it functions, right down to the level of your genes. Stress begins with something called the hypothalamus pituitary adrenal axis, a series of interactions between endocrine glands in the brain and on the kidney, which controls your body's reaction to stress. When your brain detects a stressful situation, your HPA axis is instantly activated and releases a hormone called cortisol, which primes your body for instant action. But high levels of cortisol over long periods of time wreak havoc on your brain. For example, chronic stress increases the activity level and number of neural connections in the amygdala, your brain's fear center. And as levels of cortisol rise, electric signals in your hippocampus, the part of the brain associated with learning, memories, and stress control, deteriorate. The hippocampus also inhibits the activity of the HPA axis, so when it weakens, so does your ability to control your stress. That's not all, though. Cortisol can literally cause your brain to shrink in size. Too much of it results in the loss of synaptic connections between neurons and the shrinking of your prefrontal cortex, the part of your brain the regulates behaviors like concentration, decision-making, judgement, and social interaction. It also leads to fewer new brain cells being made in the hippocampus. This means chronic stress might make it harder for you to learn and remember things, and also set the stage for more serious mental problems, like depression and eventually Alzheimer's disease. The effects of stress may filter right down to your brain's DNA. An experiment showed that the amount of nurturing a mother rat provides its newborn baby plays a part in determining how that baby responds to stress later in life. The pups of nurturing moms turned out less sensitive to stress because their brains developed more cortisol receptors, which stick to cortisol and dampen the stress response. The pups of negligent moms had the opposite outcome, and so became more sensitive to stress throughout life. These are considered epigenetic changes, meaning that they effect which genes are expressed without directly changing the genetic code. And these changes can be reversed if the moms are swapped. But there's a surprising result. The epigenetic changes caused by one single mother rat were passed down to many generations of rats after her. In other words, the results of these actions were inheritable. It's not all bad news, though. There are many ways to reverse what cortisol does to your stressed brain. The most powerful weapons are exercise and meditation, which involves breathing deeply and being aware and focused on your surroundings. Both of these activities decrease your stress and increase the size of the hippocampus, thereby improving your memory. So don't feel defeated by the pressures of daily life. Get in control of your stress before it takes control of you.
你是否睡眠品質很差 情緒焦躁易怒 容易健忘 或常感到孤獨沮喪? 別擔心,大家都有這種經驗 你可能只是壓力太大了 壓力也是有好處的 能瞬間提升爆發力和專注力 這些能力在競賽時不可或缺 在演講時也會派上用場 但如果壓力長期存在 變成每天的負擔 大腦就會開始改變 長期壓力過大 如工作過度 或常和家人起爭執 會影響大腦的大小 結構 甚至運作的方式 更會影響基因 壓力由HPA軸控制 即「下視丘-腦垂腺-腎上腺軸」 腦內的腺體及腎上腺 進行一連串交互作用 共同控制身體的壓力反應 當大腦偵測到令人緊張的環境 HPA軸便立即開始運作 釋放一種叫做可體松的荷爾蒙 使身體進入備戰狀態 但長期可體松含量過高 會嚴重傷害腦部 長期壓力下,在腦部杏仁核中 神經元連結數和活化度都會增加 而杏仁核正是情緒中樞 隨著可體松濃度升高 海馬迴的神經網也會受到破壞 學習、記憶、壓力調適等能力 都會跟著變差 海馬迴也會抑制HPA軸的運作 所以海馬迴受損 控制壓力的能力也跟著下降 除此之外 可體松還會造成大腦萎縮 也會使神經元的軸突連結減少 或造成腦前額葉萎縮 這個區域主管我們的專注力 決策力 判斷力 和社交行為 另外,海馬迴的新生細胞也會減少 學習和記憶因此變得更困難 還可能導致更嚴重的心理疾病 如憂鬱症 甚至是阿茲海默症 壓力還會影響腦部基因 一項實驗顯示 母老鼠對新生寶寶的照顧 大大影響老鼠寶寶 未來面對壓力的能力 感受滿滿母愛的小老鼠 會對壓力較不敏感 牠們腦部有較多可體松受體 能接收可體松並抑制壓力反應 與媽媽較疏離的小老鼠則相反 終其一生都對壓力很敏感 我們稱這些改變為「表徵遺傳」 基因的表現改變了 但DNA序列不變 把老鼠媽媽調換 就可消除基因表徵的改變 但還有項驚人的發現 一隻老鼠媽媽產生的影響 將會代代相傳 換句話說,這些變化是會遺傳的 不過也別太悲觀 很多方法可以消除 可體松對大腦的影響 最有效的就是運動和冥想 這些活動讓你深呼吸 並專注覺察周遭事物 運動和冥想能減緩壓力 也會增大海馬迴 因此能增強記憶力 所以別因為壓力而沮喪 在壓力控制你之前