Its symptoms, including fatigue, insomnia, irregular heartbeat, indigestion, and fever were so strong, the soldiers often had to be discharged.

症狀包含疲累感、失眠、心律不整、消化不良及發燒，而這些症狀太過嚴重以至於士兵經常只能被迫退伍。

As Hofer discovered, the cause was not some physical disturbance, but an intense yearning for their mountain homeland.

Hofer 發現，病因竟然不是身體上的異常，而是因為對家鄉強烈的盼望。

He dubbed the condition nostalgia, from the Greek "nostos" for homecoming and "algos" for pain or longing.

他稱這種現象為「nostalgia」，這個字由希臘文組成，「nostos」代表返鄉，而「algos」表示痛苦與渴望。

At first, nostalgia was considered a particularly Swiss affliction.

起初，鄉愁被認為是一種特別好發於瑞士人的痛苦。

Some doctors proposed that the constant sound of cowbells in the Alps caused trauma to the ear drums and brain.

有些醫生提出，阿爾卑斯山中持續不斷的牛鈴聲造成耳膜與大腦創傷。

Commanders even forbade their soldiers from singing traditional Swiss songs for fear that they'd lead to desertion or suicide.

指揮官甚至嚴禁士兵們唱傳統瑞士歌謠，擔心此舉會導致士兵逃亡或自殺。

But as migration increased worldwide, nostalgia was observed in various groups.

但是在全球移民數不斷上升的情況下，在不同族群中都可以觀察到思鄉病的現象。

It turned out that anyone separated from their native place for a long time was vulnerable to nostalgia.

結果顯示，任何長時間遠離故鄉的人都容易患有思鄉病。

And by the early 20th century, professionals no longer viewed it as a neurological disease, but as a mental condition similar to depression.

到 20 世紀早期，專家們才不再將思鄉病視作神經疾病，而是近似於憂鬱症的精神狀態。

Psychologists of the time speculated that it represented difficulties letting go of childhood, or even a longing to return to one's fetal state.

當時的心理學家猜測，念舊表示對童年難以割捨，或甚至是渴望回到胎兒期。

But over the next few decades, the understanding of nostalgia changed in two important ways.

但在接下來的幾十年，對「nostalgia」的理解演變成兩個重要的方向。

Its meaning expanded from indicating homesickness to a general longing for the past.

「nostalgia」的含意從一開始的思鄉擴大到對過往的憧憬。

And rather than an awful disease, it began to be seen as a poignant and pleasant experience.

這個字也開始代表深刻且喜悅的經驗，而不是糟糕的疾病。

Perhaps the most famous example of this was captured by French author Marcel Proust.

法國作家 Marcel Proust 所刻畫的例子，或許是最廣為認知的。

He described how tasting a madeleine cake he had not eaten since childhood triggered a cascade of warm and powerful sensory associations.

他描述自童年過後就沒再吃過的瑪德蓮蛋糕有多美味，且引發一連串溫暖且強而有力的感官連結。

So what caused such a major reversal in our view of nostalgia?

所以，造成我們對「nostalgia」的看法產生重大轉變的原因是什麼呢？

Part of it has to do with science.

一部分的原因與科學息息相關。

Psychology shifted away from pure theory and towards more careful and systematic empirical observation.

心理學從原本的純理論轉變為更加嚴謹與系統化的經驗觀察。

So professionals realized that many of the negative symptoms may have been simply correlated with nostalgia rather than caused by it.

所以專家們理解到，許多負性症狀可能只與思鄉病相關，而不是由思鄉所導致。

And, in fact, despite being a complex emotional state that can include feelings of loss and sadness, nostalgia doesn't generally put people in a negative mood.

事實上，儘管處在複雜的情緒狀態如失落和難過中，對過去的嚮往通常不會讓人們有負面的心境。

Instead, by allowing individuals to remember personally meaningful and rewarding experiences they shared with others, nostalgia can boost psychological well-being.

反之，藉由讓人們記住他們與別人分享對自己而言有意義的經驗，懷舊可以增進心理幸福感。

Studies have shown that inducing nostalgia in people can help increase their feelings of self-esteem and social belonging, encourage psychological growth, and even make them act more charitably.

研究顯示，引發人們心中的懷舊之情可以幫助增加自尊心與社會歸屬感，鼓勵心理上的成長，甚至能表現得更慷慨寬厚。

So rather than being a cause of mental distress, nostalgia can be a restorative way of coping with it.

所以懷舊之情可以是一種恢復精神的處理方式，而不是一項造成精神痛苦的原因。

For instance, when people experience negative emotional states, they tend to naturally use nostalgia to reduce distress and restore well-being.

舉例來說，當人們處在負面的情緒狀態時，為了減少痛苦並重新恢復幸福感，他們往往會自然而然地開始懷舊。

Today, it seems that nostalgia is everywhere, partially because advertisers have discovered how powerful it is as a marketing technique.

時至今日，「懷舊」似乎處處可見，部分原因是廣告商發現，利用懷舊作為一項行銷手法是很有影響力的。

It's tempting to think of this as a sign of us being stuck in the past, but that's not really how nostalgia works.

我們總是忍不住想把懷舊視作困在過去的象徵，但懷舊不是你所想的那樣。

Instead, nostalgia helps us remember that our lives can have meaning and value, helping us find the confidence and motivation to face the challenges of the future.

事實上，懷舊幫助我們記得人生可以活得有意義、有價值，並協助我們尋找面對未來各種挑戰的自信與動機。