About Placebo...

看板ask-why (知識奧秘)作者daze (一期一會)時間17年前 (2009/03/26 02:09)推噓6(6推 0噓 8→)

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Placebo似乎沒有想像中那麼大的效果。 Cochrane Library 的一篇Review：《Placebo interventions for all clinical conditions》（http://www.mrw.interscience.wiley.com/cochrane/clsysrev/articles/ CD003974/frame.html 縮址：http://0rz.tw/LUu02 ） Abstract： Plain language summary It has been widely believed that placebo (dummy) treatments (for example sugar tablets) are associated with substantial effects on a wide range of health problems. However, this belief is not based on evidence from randomised trials that use a placebo treatment for one group of people, while another group receives no treatment. The effect of placebo treatments was studied by reviewing more than 150 such trials covering many types of healthcare problems. Placebo treatments caused no major health benefits, although they possibly had a small effect on outcomes reported by patients, for example pain. Background Placebo interventions are often claimed to improve patient-reported and observer-reported outcomes, but this belief is not based on evidence from randomised trials that compare placebo with no treatment. Objectives To assess the effect of placebo interventions. Search strategy We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2002), MEDLINE (1966 to 2002), EMBASE (1980 to 2002), Biological Abstracts (1986 to 2002), and PsycLIT (1887 to 2002). We contacted experts on placebo research, and read references in the included trials. Selection criteria We included randomised placebo trials with a no-treatment control group investigating any health problem. Data collection and analysis Two review authors independently assessed trial quality and extracted data. We contacted study authors for additional information. Main results Outcome data were available in 156 out of 182 included trials, investigating 46 clinical conditions. We found no statistically significant pooled effect of placebo in 38 studies with binary outcomes (4284 patients), relative risk 0.95 (95% confidence interval (CI) 0.89 to 1.01). The pooled relative risk for patient-reported outcomes was 0.95 (95% CI 0.88 to 1.03) and for observer-reported outcomes 0.91 (95% CI 0.81 to 1.03). There was heterogeneity (P=0.01) but the funnel plot was symmetrical. There was no statistically significant effect of placebo interventions in the four clinical conditions investigated in three trials or more: pain, nausea, smoking, and depression, but confidence intervals were wide. We found an overall effect of placebo treatments in 118 trials with continuous outcomes (7453 patients), standardised mean difference (SMD) -0.24 (95% CI -0.31 to -0.17). The SMD for patient-reported outcomes was -0.30 (95% CI -0.38 to -0.21), whereas no statistically significant effect was found for observer-reported outcomes, SMD -0.10 (95% CI -0.20 to -0.01). There was heterogeneity (P<0.001) and large variability in funnel plot results even for big trials. There was an apparent effect of placebo interventions on pain (SMD -0.25 (95% CI -0.35 to-0.16)), and phobia (SMD -0.63 (95% CI -1.17 to -0.08)); but also a substantial risk of bias. There was no statistically significant effect of placebo interventions in eight other clinical conditions investigated in three trials or more: nausea, smoking, depression, overweight, asthma, hypertension, insomnia and anxiety, but confidence intervals were wide. Authors' conclusions There was no evidence that placebo interventions in general have clinically important effects. A possible small effect on continuous patient-reported outcomes, especially pain, could not be clearly distinguished from bias. -- 看哪，這論證是極好的：蘇格拉底是人，凡造物都難免要朽壞，所以末了我們知道，蘇格拉底總要落到死裡面了。從亞里士多德以來的每一個邏輯學家，沒有一個不歡喜這個論證的。亞里士多德明白的告訴了我們論證形式的道理，因了這個緣故，我們便尊他為邏輯學的王。 -- ※ 發信站: 批踢踢實業坊(ptt.cc) ※ 編輯: daze 來自: 140.112.212.171 (03/26 02:28)

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