Confirmation Bias and The Importance of Double-blinded Studies

About 12 years ago, I was involved in a medically supervised weight loss program.  I was very successful, having lost 120 lbs in six months.  The program wasn’t cheap and medical insurance didn’t cover it.  At the end of the weight loss portion of the program, they encouraged you to continue in the maintenance program, which involved attending bi-weekly group support sessions as well as buying their food products.  I couldn’t afford this, but then I heard about a study that they were doing with the drug, meridian.  Meridian is a drug that was prescribed for assistance in weight loss, but this study was test to see if it had an effect on weight maintenance.  Enrollment in the study would give me free access to the maintenance program, so I signed up.

The study was double-blinded, meaning that neither the participants, nor the researchers, knew who was getting the real drug and who was getting a placebo,.  Once a week, we would have our weight and vitals checked, blood drawn and given a new batch of pills to take. We would also turn in records of our calories consumption and physical exercise. Once every three weeks or so we’d see the doctor, who was the head researcher, for an exam.

The point of double-blinded studies is to remove bias, either on the part of the participant or the researchers, so that these biases don’t affect the outcome of the tests.  This is very important because bias can influence the outcome of many tests.  For example, if I knew that I was for certain getting meridian I might not try as hard to mange my diet or my exercise, thinking that the meridian would suppress my apatite.  This would skew the results because I would most likely gain weight because of my actions.  Conversely, if I knew I wasn’t getting meridian, I might try harder to mange my diet or my exercise, resulting in better weight control, again skewing the results.

Bias could also come into play on the part of the researchers.  If the doctor conducting the study knew for a fact that I was getting meridian, and I was maintaining my weight successfully, he might be willing to discount the amount of calories I was consuming or the amount of exercise I was engaged in as factors in my success and therefore skew the results.

Double-blinding allows for us to get as close as we can to the “all things being equal” point that we really want to be at when conducting studies.  This allows all factors except the thing being tested for to be controlled so that the real effect, if any,  can be seen.

I wasn’t able to complete the study because I was diagnosed with depression and needed to be put on medication for it.  This medication was contraindicated for the study so I was forced to withdraw.  

What stands out in my mind, though, was that every time I saw the doctor who ran the study, he always made a point to mention that he was sure that I was getting the real drug because I was doing so well maintaining my weight.  Even then, not knowing much about double-blind studies and bias, I found this quiet odd and a little disturbing.  I knew he was working for the company that made the drug and I wondered if he had too much of a personal stake in the results of the study.  I remember being really bothered by this.  I couldn’t put my finger on it then, but I felt that his bias could be dangerous to his patients and, if he had been my primary care physician, I surely would have switched to someone else.

This doctor’s reaction is exactly why double-blind studies are important. We, as humans, have biases about everything.  Most of the time, these biases are harmless, but when we are working in areas where knowing the truth is vital, we must remove the effect of our biases as much as is possible.

I never did find out the results of the study, but the point is moot now as Abbott Laboratories voluntarily withdrew Meridia from the market following the results of a study that linked the drug with an increased risk of heart attack and stroke.  I guess it’s a good thing I had to drop out of the study after all.





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