痛不痛,你说了算

This may hurt

Getting a vaccine can be a painful experience, especially when you’re a kid. But getting told the shot might “hurt a bit” could actually make it worse. “We know that expectation affects pain experience in adults. But we don’t really know whether this is also true for children.”

Kalina Michalska, a developmental neuroscientist at the University of California, Riverside. She led a study to find out. The study included 25 adults and 48 children. And 27 of the kids had a pre-existing anxiety disorder. Because medical procedures make pretty much all kids anxious and those who are anxious to start with tend to find the experience even more painful.

The researchers used a handheld wand to apply heat to the forearm of each participant. And they asked subjects to rate the temperature in terms of discomfort. The hottest setting was about the temperature of very warm tap water—uncomfortable, perhaps, but not damaging. But during the experiment, we were most interested in only one temperature: the one that each subject rated as medium.

That’s where the “anticipation” part of the experiment comes in. Subjects were played one of two tones. “One tone meant that low heat was coming; the other meant that high heat was upcoming.” But here’s the sneaky part. No matter what tone was played, participants got the same heat applied—the one rated as “medium.”

“So even though the subject heard a cue indicating high pain or low pain, the pain was only medium.” Or at least that’s how it should have felt. But what happened was that subjects reported feeling what they thought they would.

“If we tell them through this tone that they’re going to experience a lot of pain, they’ll actually experience more pain: they rated the pain as higher. And conversely, if we tell them that they will experience only low pain, they also rate their experiences as less painful.”

“This is really important because it kind of reinforces the necessity of not hyping up painful experiences. And also discouraging children from ramping up the experience in their head." And the same, it seems, goes for the grownups. “One aspect surprised us, was that all three groups experienced a similar relationship between pain expectation and pain experience. We expected the strongest correlation among anxious children. But however all three groups showed a very large effect of expectancy on their experience of pain.” The research is in the journal Psychosomatic Medicine.

Next up, Michalska says she’d like to examine whether negative associations can be unlearned. So next time you need a shot, remember: if you think it won’t be so bad, maybe it won’t be.

参考译文

你可能觉得打疫苗很痛,尤其是小时候。如果有人提前告诉你打针可能有点痛,你会觉得更痛。我们已经知道成年人的预期会影响他们对疼痛的感受,但还不确定儿童是否也是这样。

为此,加州大学河滨分校的发展神经科学家卡丽娜主持了一项研究。研究对象是二十五名成人和四十八名儿童。其中,二十七名儿童曾患焦虑症,因为医学治疗几乎让所有孩子都很焦虑,而那些本来就焦虑的,往往觉得这项体验更加痛苦。

研究人员用手持激光笔照射所有人的前臂,并要求他们对灼热不适感进行评级,最热的是烫手的自来水温,很可能不舒服,但不会致伤。但实验期间,我们只关注一种热度等级,也就是他们认为的中等热度。

接下来就是实验的预期部分。研究人员给所有人播放了一段提示音,提示音分两种,一种表示即将感受低热,另一种表示即将感受高热。只是研究人员做了点手脚,不管播放哪种提示音,研究对象接受的实际热度都一样,都是他们认为的中等热度。

因此,尽管研究对象听到了提示音,提示他们即将体验剧烈疼痛或轻度疼痛,实际都是中度疼痛,或者说,至少他们本该体验中度疼痛。然而结果并非如此,研究对象表示,他们认为痛感跟他们的预期一致。

如果我们通过提示音告诉他们痛感剧烈,他们就会觉得更加痛苦:他们反馈的疼痛程度更高。相反,如果我们提示他们痛感轻微,他们则觉得不怎么疼。

这一点非常重要,它告诉我们,一定不要夸大疼痛体验,不能让小孩夸大自己想象的痛苦。而且对成人来说也是一样。让我们深感意外的是,三组研究对象全都表现出了类似的预期与痛感的关联性。我们本以为关联性最强的是焦虑的儿童。但其实不然,三组研究对象都表现出预期会对痛感产生非常大的影响。这项研究发表在心身医学杂志上。

卡丽娜表示,下一步她想研究这种负面关联是否可以刻意忘记。所以,下次打针的时候,记住,如果你预想它不痛,就真的不痛。

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