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Chances are that you or someone you care about has experienced depression.
您或您关心的人可能经历过抑郁症。
It's one of the most common mental health problems in the US.
这是美国最常见的一种心理健康问题。
Around 16% of American adults will suffer from depression at some point in their life.
大约16％的美国成年人会在生命的某个阶段患上抑郁症。
Given how much we talk about and treat depression, it might seem like we've got it figured out, from a scientific perspective.
我们经常谈论抑郁症及其治疗方法，从科学角度来看，我们似乎已经把抑郁症搞明白了。
But we do not understand as much about it as you might think.
但是我们并不像你想象的那样对它非常了解。
Especially what's actually going on in your brain when you're depressed.
尤其是当你情绪低落时，你的大脑里到底发生了什么。
Doctors have defined depression, or at least agreed on a set of criteria to diagnose it.
医生已经界定了抑郁症，或者至少认同一套诊断标准。
The Diagnostic and Statistical Manual for Mental Disorders, also known as the DSM, is the handbook healthcare professionals use to diagnose mental disorders.
《精神障碍诊断和统计手册》（也称DSM）是医疗保健专业人员用来诊断精神障碍的手册。
And the latest edition of the DSM lays out two key symptoms of depression.
最新版的DSM列出了抑郁症的两个主要症状。
The first is feeling sad or depressed.
第一个是感到悲伤或沮丧。
But many depression sufferers experience this more as a lack of feeling, or numbness, rather than sadness.
但许多抑郁症患者体会到更多的是缺乏感觉或麻木，而不是悲伤。
The second is a loss of interest or pleasure in activities that are normally enjoyable.
第二个症状是对通常令人愉快的活动失去兴趣或愉悦感。
You have to have at least one of these key symptoms, as well as 3-4 additional symptoms consistently, to be diagnosed with depression.
你必须至少出现这些关键症状中的一个，以及3-4个持续存在的额外症状，才能被诊断为抑郁症。
Additional symptoms can include unpleasant things like: feeling worthless, difficulty sleeping or sleeping too much, difficulty concentrating and making decisions, or suicidal thoughts.
其他症状包括下列这些令人不快的事情：无价值感，睡眠困难或睡眠过多，难以集中注意力和决策困难，或有自杀念头。
Not all of your symptoms need to be severe, but as a group they can make it harder for you to function at work or school, in your relationships, or just in life.
并非所有症状都需要很严重，但作为一个症状群，它们会使你更难应对工作、学校、人际交往或生活中出现的各种情况。
We know that depression isn't simply a bad mood that you can snap out of — something is not functioning correctly in your brain.
我们知道，抑郁症并不只是大脑无法正常运作而突然出现的一种不良情绪。
The question is what?
问题是那是什么？
One widespread impression among the public is that depression is caused by having too little serotonin.
公众普遍认为抑郁症是由血清素过少而引起的。
But that's an oversimplification at best.
但这样描述过于简单化了。
Serotonin is a neurotransmitter — a chemical that neurons use to signal each other.
5-羟色胺是一种神经递质，是神经元用来互相发出信号的化学物质。
When a neuron signals its neighbor, it releases a neurotransmitter, like serotonin, into the synapse — the space between itself and its neighbor.
神经元向其临近神经元发出信号时，会向突触释放5-羟色胺等神经递质，突触神经元与其临近神经元之间的间隙。
The serotonin molecules diffuse across the synapse and bind to their receptors on the neighboring neuron, transmitting the signal.
5-羟色胺分子通过突触扩散，并与邻近神经元上的受体结合，传递信号。
Then the signalling neuron reabsorbs — or re-uptakes — its serotonin.
随后，发出信号的神经元重新吸收它的5-羟色胺。
Some of the most commonly used medications for depression are selective serotonin reuptake inhibitors, or SSRIs.
一些最常用的抑郁症治疗药物是选择性5-羟色胺再摄取抑制剂或SSRIs。
SSRIs reduce the reuptake of serotonin, which increases the amount of serotonin hanging around synapses.
SSRIs减少了对5-羟色胺的再摄取，从而增加了突触周围的5-羟色胺含量。
But how these medications work and sometimes don't work show that a lack of serotonin isn't the only thing happening in the depressive brain.
5-羟色胺是这样发挥药效的，但有时它却不起作用，这说明抑郁症患者的大脑中并不只是缺乏5-羟色胺。
If that were true, you'd expect that SSRI medications to work pretty quickly, and to work for everyone with depression — but they don't.
如果这是真的，你会期望SSRI药物能很快发挥作用，并且对每个抑郁症患者都有效，但其实并不是这样。
Even though serotonin concentrations may go up right away when you take an SSRI, it can still take weeks for people to start feeling better.
即使服用SSRI后5-羟色胺浓度可能会立即升高，但仍然需要数周时间才能让患者感觉有所好转。
That is, if they even start feeling better at all.
也就是说，如果他们开始感觉病情好转的话。
SSRIs simply don't work for all patients.
SSRIs并不适用于所有患者。
Research has identified a few other potential factors that could help us better treat depression.
研究发现了一些其他的潜在因素，有助于我们更好地治疗抑郁症。
First off, serotonin isn't the only neurotransmitter that plays a role.
首先，5-羟色胺不是唯一起作用的神经递质。
Research has shown that at least 5 other neurotransmitters could be involved, all of which serve many different functions in the brain and elsewhere in the body — it's complicated!
研究表明，至少还有5种神经递质参与其中，所有这些递质在大脑和身体其他部位发挥着许多不同的功用，这很复杂！
And the structure of our brains matters too — not just the chemicals inside them.
除了大脑内部的化学物质外，大脑结构也很重要。
Certain regions of the brain, and the connections between them, have been shown to be altered in depression.
大脑的某些区域以及它们之间的联系已被证实在抑郁症患者脑中发生了改变。
The amygdala, which helps us process emotions, and the hippocampus, which has a role in memory storage, are among the brain regions that undergo structural changes in some patients with depression.
帮助我们处理情绪的杏仁核和在记忆储存中起作用的海马体，是在一些抑郁症患者中发生结构变化的脑区。
Changes like having a different size compared to people without depression, though we're not sure what that means exactly yet.
与没有抑郁症的人相比，脑区大小发生了改变，尽管我们还不确定这究竟意味着什么。
And rather than merely changing the levels of certain neurotransmitters, studies have shown that antidepressants can actually help new neurons grow in certain parts of the brain.
研究表明，抗抑郁药实际上有助于新神经元在大脑的某些部位生长，而不仅仅是改变某些神经递质的水平。
Which may be one reason why SSRI medications typically take so long to work.
这也许是SSRI药物通常需要很长时间才能起作用的一个原因。
Your brain could be growing new neurons, not just responding to a short-term change in chemical messengers.
你的大脑中可能正在生长新的神经元，而不仅仅是对化学递质的短期变化做出回应。
There's likely a genetic component to depression as well.
抑郁症也可能存在遗传因素。
There is some evidence that depression can run in families, though the association isn't particularly strong.
有一些证据表明，抑郁症可以在家族中遗传，尽管这种联系并不是特别强烈。
A 2018 genome-wide study sampled a huge pool of genes in people with and without depression.
2018年开展的一项全基因组研究中，对患有和不患有抑郁症的人进行了大量基因取样。
It found 44 variants that seem to be associated with depression.
结果发现了44种与抑郁症相关的变异。
These so-called “genes of interest” included genes previously shown to have a role in the growth of neurons — as well as some surprises, like genes previously shown to be involved in immune system function.
这些所谓的“基因区”包括已经被证实在神经元生长中发挥作用的基因，以及一些令人惊讶的基因，如已被证实与免疫系统功能有关的基因。
But it's unlikely that a particular gene or genes cause depression on their own.
但是，一个或多个特定基因不太可能单独引发抑郁症。
More likely, it could be the result of how your personal set of genes interacts with your environment and your experiences.
更有可能是因为你个人的一组基因与你所在的环境和经历相互作用的结果。
Some studies have found that variants in certain genes can interact with major stressful events in childhood to affect the rate of depression in adults.
一些研究发现，某些基因变异与童年时的主要压力事件相互作用，从而影响成年后患上抑郁症的几率。
But not all studies find such strong links between our genes and our environment.
但并不是所有研究都发现我们的基因和环境之间有如此强的联系。
It's still an active area of study.
这仍然是一个活跃的研究领域。
So depression is hard to figure out.
所以，很难搞明白抑郁症。
There are so many factors involved, and they all interact with each other — from genetics and environment, to the chemistry and structure of the brain.
涉及的因素很多，它们都相互作用，从遗传和环境到大脑的化学组成和结构。
The good news is that even though we don't entirely understand how depression works, we still have ways to treat it that help lots of people.
好消息是，尽管我们并不完全了解抑郁症的运作机制，但我们仍然有办法对它进行治疗，帮助很多患者。
You don't have to know exactly how an existing medication or treatment works to know that it does work — that patients may respond to it and feel better.
你不必确切地知道现有药物或治疗是如何发挥作用的，只要知道它确实有用就行了——患者会对治疗有反应，感觉病情好转。
Meanwhile, scientists are still working to tease out the many, intertwined causes of depression to develop new treatments.
与此同时，科学家们仍在努力梳理引发抑郁症的相互交织的许多原因，以开发新疗法。
So there's hope on the horizon.
希望就在眼前。
Even when you can't see it.
即使还看不见它。
Thanks for watching this episode of SciShow Psych, which was supported by our community of patrons.
感谢收看本期《心理科学秀》，我们的节目得到了赞助人社区的支持
To learn more, check out patreon.com/scishow.
要了解更多信息，请访问patreon.com/scishow。
