来源：《新科学家》
原文见刊日期：2023年5月13日
These days, we are increasingly aware that mental health problems can be as debilitating as physical ones. Unfortunately, much of what we thought we knew about what causes mental illness has recently turned out to be wrong.
如今，我们越来越意识到，心理健康问题和身体问题一样会使人衰弱。不幸的是，我们本以为知道的导致精神疾病的原因，最近却被证明是错误的。
In a way, this shouldn’t be surprising, says Allen Frances at Duke University in North Carolina, lead author of a major US psychiatry textbook, the Diagnostic and Statistical Manual of Mental Disorders IV. “The brain is the most complicated thing in the known universe, and it reveals its secrets very slowly,” he says.
北卡罗来纳州杜克大学的艾伦·弗朗西斯是美国主要精神病学教科书《精神障碍诊断与统计手册IV》的第一作者，他说，从某种程度上说，这并不奇怪。“大脑是已知宇宙中最复杂的东西，揭示其秘密的速度非常慢。”
A couple of decades ago, we seemed on the verge of unlocking the secrets of several mental health conditions. The cause was thought to be irregular levels of various brain chemicals, which could be remedied with drugs. Depression, for example, was thought to stem from a lack of the brain signalling chemical serotonin, partly because the most common kind of antidepressants raise levels of this compound. Genetic studies also found that people with depression were more likely to have a gene variant that lowers serotonin.
几十年前，我们似乎即将揭开几种心理健康疾病的秘密。原因被认为是大脑中各种化学物质水平不正常，这可以用药物来补救。例如，抑郁症被认为是由于缺乏大脑信号化学物质血清素，部分原因是最常见的抗抑郁药会提高这种化合物的水平。基因研究还发现，抑郁症患者更有可能携带降低血清素的基因变异。
But this neat picture turned out to be a mirage. The latest evidence suggests that low serotonin isn’t a cause of depression, and many early genetic studies that implicated single brain chemicals as a cause of specific conditions were carried out using scientific methods now considered to have been flawed.
但这幅整洁的画面最终被证明是海市蜃楼。最新的证据表明，低血清素不是抑郁症的原因，许多早期的基因研究表明，单一的大脑化学物质是导致特定疾病的原因，但这些研究使用的科学方法现在被认为是有缺陷的。
Mental health conditions do have a strong heritable component. But the genetics are complex. The most recent genetic studies show that more than 100 gene variants influence our risk of depression, for example, each with only a tiny impact.
心理健康疾病确实有很强的遗传因素。但基因是复杂的。例如，最近的基因研究表明，超过100种基因变异会影响我们患抑郁症的风险，但每种变异的影响都很小。
Every other mental health condition investigated so far is similarly influenced by multiple genes. And many of the same genes are involved in predisposing people to what are usually thought of as very different conditions, including depression, anxiety and obsessive compulsive disorder. “We’ve given up on a small number of genes explaining any mental illness,” says Frances.
到目前为止，所有其他被研究的心理健康疾病都同样受到多种基因的影响。而且，许多相同的基因都与人们容易患上通常被认为非常不同的疾病有关，包括抑郁症、焦虑症和强迫症。“我们已经放弃了用少数基因来解释任何精神疾病，”弗朗西丝说。
The genetic revelations have lent support to a recent idea that all mental health conditions may have their roots in a common underlying cause. The idea is that these gene variants together make the brain more vulnerable to mental illnesses. Perhaps which condition someone develops depends on different external triggers or even chance events.
基因方面的发现支持了最近的一种观点，即所有的精神健康疾病可能都有一个共同的潜在原因。这个观点是，这些基因变异共同使大脑更容易受到精神疾病的影响。也许一个人的病情取决于不同的外部触发因素，甚至是偶然事件。
What that vulnerability may consist of isn’t clear. In April, a large brain-scanning study suggested it could be down to insufficient “pruning”, the process of getting rid of unhelpful connections between brain cells, which begins in early childhood but intensifies in adolescence. “It’s a single underlying neurobiological factor,” says Barbara Sahakian at the University of Cambridge.
这个弱点可能由什么组成尚不清楚。今年4月，一项大型脑部扫描研究表明，这可能是由于“修剪”不够，即去除脑细胞之间无用连接的过程，这一过程始于童年早期，在青春期增强。“这是一个单一的潜在神经生物学因素，”剑桥大学的芭芭拉·萨哈基安说。
This is unlikely to be the final word, though, especially as brain-scanning studies have a long history of producing divergent results that even experts can’t agree on. Perhaps the most important thing to understand about mental illness, then, is how much we have yet to understand.
不过，这不太可能是最终结论，尤其是考虑到大脑扫描研究长期以来产生的有分歧的结果，甚至连专家都无法达成一致。那么，了解精神疾病最重要的事情可能是，我们还没有了解多少。