But, what exactly is going on inside of a depressed person?

但是，到底憂鬱症患者的內在發生了什麼事呢？

Is there a biological basis for these intense feelings of sadness?

這些強烈的悲傷情緒有任何生物學上的根據嗎？

In the past, depression was often described as simply a "chemical imbalance" in the brain.

在過去，憂鬱症常常只被描述成腦分泌不平衡。

Specifically, scientists believed that a lack of the neurotransmitter, serotonin, was to blame, which is often referred to as the "feel good" chemical.

科學家們相信主要原因是缺乏神經傳遞介質，血清素；血清素常被稱作是「令人愉悅」的物質。

However, the only real evidence for this was that when some depressed people were prescribed drugs which increased serotonin levels, it helped alleviate their symptoms.

然而，這個理論唯一的證據是，當某些憂鬱的人服用了可以增加血清素濃度的處方藥時，那些藥物可以減輕他們的憂鬱症狀。

But while chemicals most certainly are involved, this view doesn't really capture just how complex depression is.

但是當不同的物質被包含在其中時，這個觀點似乎不能真正的解釋憂鬱症有多複雜。

In recent years, scientists began to notice that the brain cell growth and connections may actually play a larger role.

最近幾年，科學家們開始注意到事實上大腦細胞的成長和連結可能扮演著重要的角色。

When we look at the brain of a depressed person, studies show that the hippocampus tends to be much smaller than average.

當我們觀察憂鬱症患者的頭腦時，研究發現他們的海馬迴通常較一般大小小的多。

Other areas of the brain are also physically affected, but this region in particular controls memory and emotion.

其他大腦的區塊也會受到生理上的影響，但是海馬迴主要是特別控制記憶和情緒的。

And the longer a person has been depressed, the smaller the hippocampus becomes.

而且人經歷沮喪的時間越長，海馬迴就變得越小。

The cells and networks literally deteriorate.

那些細胞和網絡逐漸地退化。

It turns out that stress may actually be a main trigger in the decrease of new neurons in this area of the brain.

原來是因為壓力，可能是造成大腦內這個區域新細胞減少的主因。

In fact, studies have shown that when this region of the brain is regenerated and new neurons are stimulated, mood improves.

事實上，研究顯示當這個區塊在新生細胞而且新細胞被刺激的時候，情緒會變得更好。

Interestingly, many modern drugs, including those which affect serotonin levels, have an indirect effect on the growth of brain cells.

有趣的是，很多現代的藥物，包含那些會影響到血清素數量的，對於腦部細胞的成長會造成間接的影響。

This is likely why serotonin-based drugs seem to help some patients - but not for the reasons we once thought.

這可能是為什麼會影響血清素的藥物會對某些病患有所幫助，但並不是基於我們曾經認為的理由。

Instead, they promote the release of other chemicals, which ultimately stimulate neurogenesis, or the growth of new neurons.

取而代之的是，這些藥物有助於釋放其他物質，最終會刺激神經生成或是新神經細胞成長的物質。

Knowing this, some scientists now believe focus should be on drugs which directly affect neurogenesis.

知道了這一點，某一些科學家現在相信應該要著眼於直接影響神經生成的藥物。

But while your neurons and chemicals may be the direct influencers, many genetic factors have been discovered as well.

但是當你的神經和激素可能是直接的影響者，很多基因的因素也會被發現。

One particular study found that a variation in the serotonin transporter gene leaves individuals more vulnerable to depression.

有一個特定的研究發現血清素內傳輸基因的差異會讓個體對於沮喪感到更加脆弱。

Every individual has two copies of the gene - one from each parent.

每個個體都有兩套基因，分別來自其父母。

And this gene can either be short or long.

這個基因可以是短的或是長的。

After tracking 800 young adults over 5 years,

在追蹤了 800 個年輕成人超過 5 年後，

the studies revealed that 33% of individuals with one short version became depressed after stressful life events and people with two short genes fared even worse.

研究顯示其中 33％ 有一套較短基因的人，在面臨壓力後會變得沮喪，而有兩套短基因的人甚至更糟糕。

On the other hand, those with two "long" genes were much less likely to become depressed with similar life stress.

另外一方面，那些有兩套比較長的基因的人在相同壓力下比較不容易變得沮喪。

Many other genes have been identified which increase the likelihood of depression, too.

許多其他的基因也被證實增加了導致憂鬱的可能性。

And it makes sense when you consider that depression and bipolar disorder both run in families.

而且當考慮到憂鬱症和躁鬱症的人會同時出現在一個家族裡，這就說得通了。

Studies of identical twins show that if one has bipolar disorder, the other has a 60-80% chance of developing it, too.

研究顯示同一對雙胞胎如果其中一個有躁鬱症的話，另外一個也有的機率是 60-80％。

So while the true cause or causes of depression have yet to be pinned down precisely, and trust us, there is a HUGE list of other variables that studies suggest may come in to play.

所以當真正造成憂鬱症的原因還沒被準確的確認時，相信我們，研究顯示還有許多其他的變因可能會引起作用。

It's important to remember that depression is a disease with a biological basis, along with psychological and social implications.

重要的是，要記得憂鬱症是一種基於生物學的基礎上，包含心理學和社會意涵的疾病。

It's not simply a weakness that somebody should get over, or even something that we have a say in.

它並不簡單的只是一個某人需要克服的弱點或是我們可以任意言述的。

And just like heart disease, or cancer, shedding light onto the subject is of the utmost importance, in order to bring funding and proper research.

就像心臟疾病或是癌症，為了募得資金和適當的研究，讓研究主體可以被清楚的瞭解是很重要的。

But, is depression only a human phenomenon?

但是，憂鬱症只是人類會有的現象嗎？

We look into the question "Do Dogs Get Depressed?" in our latest AsapTHOUGHT video,

在最新的 AsapTHOUGHT 影片中，我們開始研究狗是否也會感到憂鬱，

and discover the many studies done to understand depression among other species, including your pets at home.

並且發現了許多關於了解其他狗狗憂鬱症的研究，其中包含你家的寵物。

You can click the link in the description for that video.

你可以在資訊欄點擊影片的連結。

You can also check out the book “Animal Madness” by Laurel Braitman which touches on the subject.

也可以瀏覽一下 Laurel Braitman 寫的《Animal Madness》，這本書也在探討這個主題。

In fact, you can get it for free from our friends at Audible by going to audible.com/asap.

其實，你可以在 "audible.com/asap" 上得到免費的版本。

Audible is the leading provider of audiobooks with over 150,000 downloadable titles across all types of literature.

Audible 是主要的有聲書提供者，有著超過十五萬可以被下載各式各樣的文學作品。

You can download this audio book or another of your choice, for free, at audible.com/asap.

你可以在 "audible.com/asap" 下載這本有聲書或是選擇其他免費的書籍。

And with a subscription you get one free book a month!

並且只要訂閱就可以得到一本免費的有聲書一個月！

Special thanks Audible for making these videos possible!

特別感謝 Audible 讓我們可以製作這些影片！

If you think you're suffering from depression, we have included some resources and more information in the description.

如果你認為你正在受到憂鬱症的困擾，我們會把一些資源和資訊放在資訊欄。

And subscribe for more weekly science videos!

訂閱更多每週科學影片吧！