The Placebo Effect
Chester J. Zelasko, Ph.D. | April 8, 2008

The Internet is filled testimonials as the basis for the benefits of many products. Weight loss. Super juices. Colon cleansing. Lowering cholesterol. Better balance. No matter how many testimonials are used, it’s not good enough. Why not? Because you can never underestimate the placebo effect. If someone believes something is good for them, it will be. As incredible as that sounds, it’s true. Check any scientific study and you’ll find some of the people who got the placebo reported an improvement in whatever condition was being tested.

Recently, a study was published that illustrated the point better than any other study I’ve read. It was not a complicated research design, but it was effective in making its point. Let’s take a look at the study.

The Study
Researchers recruited subjects through an online ad in the Boston area (1). The subjects were told that the purpose of the study was to evaluate a new faster-acting pain medication similar to codeine. In actuality, the researchers wanted to examine whether the cost of a medication influenced the expectation of how well the medication worked.

The 82 subjects who volunteered for the study were paid $30 for their participation. Paying subjects is not unusual--many a graduate student earned money that way to pay the rent. The subjects were divided into two groups. Group One received a pain pill they were told cost $2.50 per dose while Group Two was told the pill cost only $0.10. In reality, both groups received the exact same pill.

Pain is very subjective. What puts one person on the floor writhing in pain seems to not affect another. To individualize the response to pain before and after taking the pills, subjects were exposed to electric shocks on their wrist from very light to the maximum they could stand. The researchers had the subjects rate the pain on a computerized visual analog scale from “no pain at all” to “the worst pain imaginable.” The responses were converted to a 100-point scale. The difference in scores before and after taking the pain pill was used in the analysis.

The subjects who got the more expensive pill got better pain relief than those who got the cheaper one--85% to 61%. In fact, as the researchers increased the shock, the difference became more pronounced; those receiving the more expensive pill claimed better relief than those taking the cheaper pill. That confirmed the researchers hypothesis that how much a pill costs can influence how well a medication works.

The Twist
There’s one more thing you need to know. All subjects received placebos--there were no active pain-relieving medications administered at all. Remember, 85% of the subjects who were told they received the more expensive medication got pain relief as did 61% of those who got the cheaper medication. All from a placebo. This is the most powerful example of the placebo effect I’ve seen in the scientific literature.

This study illustrates why double-blind, placebo-controlled (DBPC) trials are critical to test the effectiveness of any food, supplement, vitamin, mineral, or drink. The placebo effect can be profound. There’s only one way to overcome it: the design of the study must be double-blind. That means the subjects can’t know what they’re getting, and the researchers can’t know what they’re giving them. The active ingredients have to be administered in a random order with some people getting no active ingredients at all; that’s the placebo-controlled aspect. Of course people will try to guess--some subjects will be convinced that they’re getting the active ingredient while others will be convinced they aren’t. They cancel out each other, so that in the end if there is an effect, it will be discovered.

That’s not to say that everything can be tested via DBPC trials. Diets are a perfect example. Because they last so long, unless every item the subjects will eat is prepared in a laboratory, people will know which diet they’re on. But when it’s possible, the DBPC trial is the standard by which every product should be evaluated.

Bottom Line
Never underestimate the placebo effect. If someone believes that something will help them, whether it contains an active ingredient or not, it often will; that’s why I take testimonials with a big helping of salt. But someone’s belief that a product worked isn’t the standard on which health products should be evaluated--products must be tested in a way to minimize the placebo effect. If they’re not, there’s one adage that fits: if it sounds too good to be true, it usually is.

  1. Waber RL, et al. Commercial Features of Placebo and Therapeutic Efficacy. JAMA. 2008; 299(9):1016-17.
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