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A placebo is a dummy treatment, such as a sugar pill. In pain studies, placebos can reduce the pain people report and also dampen activity in the brain areas that process pain, even though they contain no active drug.

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The word placebo is Latin for “I shall please”. One of the first clues that the effect is physical came in 1978, when Jon Levine and colleagues studied patients recovering from wisdom tooth removal. They gave them a placebo and naloxone, a drug that blocks the effect of endorphins, the body's own painkilling chemicals. In patients who had responded to the placebo, naloxone increased the pain, which suggested that the placebo relief came from endorphins. In 2004 Tor Wager and colleagues used brain scans to show that a placebo painkiller reduced activity in pain-processing regions during a painful stimulus. Expectation works the other way too: in the nocebo effect, from the Latin for “I shall harm”, expecting harm makes symptoms worse. None of this means the pain was imaginary, or that placebos can replace effective treatment.

Türkçe oku
Plasebo, şeker hapı gibi, içinde hiçbir etkin madde bulunmayan göstermelik bir tedavidir. Ağrı araştırmalarında plasebolar, kişilerin hissettiği ağrıyı azaltabiliyor, hatta beyinde ağrıyı işleyen bölgelerin etkinliğini düşürebiliyor.

Plasebo sözcüğü Latincede “memnun edeceğim” demektir. Etkinin bedende gerçek bir karşılığı olduğuna dair ilk ipuçlarından biri 1978'de ortaya çıktı. Jon Levine ve arkadaşları, yirmilik dişi çekilmiş hastalara plasebo ve nalokson verdi. Nalokson, vücudun kendi ürettiği ağrı kesici maddeler olan endorfinlerin etkisini engelleyen bir ilaçtır. Plaseboya yanıt veren hastalarda nalokson ağrıyı artırdı; bu da plasebonun sağladığı rahatlamanın endorfinlerden kaynaklandığını düşündürdü. 2004'te Tor Wager ve arkadaşları beyin taramalarıyla şunu gösterdi: Ağrı kesici diye plasebo verilen kişilerde, canlarını yakan bir uyarı sırasında beynin ağrıyı işleyen bölgeleri daha az etkinleşiyordu. Beklenti ters yönde de işler: Latincede “zarar vereceğim” anlamına gelen nosebo etkisinde, zarar görmeyi beklemek belirtileri ağırlaştırır. Bütün bunlar ağrının hayal ürünü olduğu ya da plasebonun etkili bir tedavinin yerini tutabileceği anlamına gelmez.

Sources and further reading

Background reading: Placebo
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