

© flickr & zenera
治療への期待が実際の効き目を高めるプラセボ効果はすでに明らかだが,逆に治療に期待しないと効果が低くなることが鎮痛薬による実験で検証された。被験者22名に一定量のオピオイド薬を点滴し続け,足に熱刺激を加えた際の鎮痛効果が,痛みのスコア化と脳の機能的MRIで評価された。鎮痛効果は,点滴開始を被験者に知らせる前と比べ知らせた後に倍増し,逆に実際は点滴を続けているのに止めたと告げた後はほとんど消失した。期待しないことの否定的影響は,有効な治療法を探し続ける慢性痛患者などで懸念されるという。(吉田素子)
The Placebo Effect: Expecting the Best, Fearing the Worst
Poor expectations of treatment can override all the effect of a potent pain-relieving drug, a brain imaging study at Oxford University has shown.
In contrast, positive expectations of treatment doubled the natural physiological or biochemical effect of the opioid drug among the healthy volunteers in the study.
The study of the placebo effect -- and its opposite the nocebo effect -- is published in Science Translational Medicine. The findings suggest that doctors may need to consider dealing with patients’ beliefs about the effectiveness of any treatment, as well as determining which drug might be the best for that patient.
‘Doctors shouldn’t underestimate the significant influence that patients’ negative expectations can have on outcome,’ says Professor Irene Tracey of the Centre for Functional Magnetic Resonance Imaging of the Brain at Oxford University, who led the research.
‘For example, people with chronic pain will often have seen many doctors and tried many drugs that haven’t worked for them. They come to see the clinician with all this negative experience, not expecting to receive anything that will work for them. Doctors have almost got to work on that first before any drug will have an effect on their pain.’
The placebo effect describes the improvements seen when patients -- unknowingly -- are given dummy pills or sham treatments but believe it will do them good. This is a very real physiological effect; it is not just about patients ‘feeling’ better. The nocebo effect is the opposite: patients see poorer outcomes as the result of doubts about a medical treatment.
[単語和訳]
Placebo Effect:プラセボ効果
override:~を無効にする potent:強力な pain-relieving drug:鎮痛薬 brain imaging:脳イメージング
In contrast:一方 doubled:~を2倍にした physiological:生理学的な biochemical:生化学的な opioid drug:オピオイド薬
nocebo effect:ノセボ効果 Translational:トランスレーショナル(基礎研究を臨床につなげることを目指した)(Science Translational Medicineは雑誌名)effectiveness:有効性
underestimate:~を過小評価する Functional Magnetic Resonance Imaging:機能的磁気共鳴画像法
chronic pain:慢性痛 clinician:臨床医 have got to:~しなければならない work on:~に(向き合って)対処する
unknowingly:知らされないまま dummy pills:偽薬 sham treatments:偽治療