Not-so-random errors

This is very interesting. The assertion is that studies which use randomized controlled trials, the most common form of medical trial, may not be nearly as accurate as had been previously assumed:

A randomized controlled trial (RCT) is based on the idea that if you randomly-assign subjects to an experimental group that receive an intervention or to a control group that does not, then any known or unknown differences between the groups that might bias the study are as likely to affect one group as another.

While that sounds good in theory, in practice a RCT can often introduce its own set of biases and thus undermine the validity of the findings.

For example, a RCT may be designed to determine if dietary changes may prevent heart disease and cancer. Investigators identify patients who meet certain selection criteria, e.g., that they have heart disease. When they meet with prospective study participants, investigators describe the study in great detail and ask, "If you are randomly-assigned to the experimental group, would you be willing to change your lifestyle?" In order to be eligible for the study, the patient needs to answer, "Yes."

However, if that patient is subsequently randomly-assigned to the control group, it is likely that this patient may begin to make lifestyle changes on their own, since they have already been told in detail what these lifestyle changes are. If they're studying a new drug that only is available to the experimental group, then it is less of an issue. But in the case of behavioral interventions, those who are randomly-assigned to the control group are likely to make at least some of these changes because they believe that the investigators must think that these lifestyle changes are worth doing or they wouldn't be studying them.

In short, such trials may not be anything like as scientifically rigorous as doctors and researchers would have us believe. When that problem is combined with the issues of confirmation bias and sponsorship sources, it's quite possible that the results of any given study amount to little more than wasted time and money.