Non-specific factors in randomized
clinical trials: some methodological
|Definition of placebo and placebo effect|
|Coloured drugs as example of a
|Research into placebo effects and
Anton de Craen's study tried to find out whether identical-appearing tablets become more or less effective depending on whether a positive or neutral attitude is expressed by the practitioner giving them. In fact, contrary to what they expected, this appeared not to influence the results. This led them to believe that expectancy must be only one among many significant non-specific factors that influence outcome. The researchers believe that practitioners need to know more about these factors, and that therefore we should develop the kind of research that can identify all the circumstances that determine a maximal treatment effect. We can only agree with the authors that this is an important issue, given what Angela Clow tells us in her chapter about the beneficial physiological changes that result when these circumstances are working well. The chapter raises important questions about how to research the impact of beliefs and the whole range of influences highlighted by our previous authors.
The 1948 trial of streptomycin for the treatment of pulmonary tuberculosis is generally considered to be the first randomized clinical trial (Streptomycin in Tuberculosis Trials Committee 1948). Although other trials have been reported earlier, the trial certainly heralded in a new era in clinical medicine (Vandenbroucke 1987). Until then, most therapies were not judged to be efficacious on the basis of documented observations and comparisons but on pathophysiological rationales provided by authoritative experts (Feinstein 1985). The major advantage of randomized