The Placebo Effect: Why It’s Useful in Clinical Trials

June 6, 2017

Medical advancements rely heavily on clinical trials and research to prove the safety and efficacy of a new treatment, medication or device. Researchers test the new treatment idea in the lab, and in many cases, on animals before expanding their research to include humans.

Small groups of human participants can begin a clinical trial, but the new treatment must measure against a control group. The researchers may introduce a placebo-controlled group to compare and contrast the results of the new medical strategy. The placebo can also have an effect on the trial’s results.

The placebo looks identical to the treatment or medication. Researchers may administer the placebo as an injection, topical or oral treatment. It does not contain any of the experimental drugs, but some patients do report positive or negative outcomes known as the placebo effect.

How Researchers Use Placebos in Clinical Trials

A clinical trial may involve either blind or double-blind studies. In a blind study, the participants are unaware if they are receiving the placebo. In a double-blind study, both the participants and the scientists are unaware of who is in the placebo group. A double-blind study removes any biases that may skew the results of the trial.

Since a placebo does not contain any active ingredients, why do researchers use it as opposed to a “no treatment” group? Participants in placebo-controlled groups report experiencing greater outcomes during the trial, whether negative or positive. These are not imaginary outcomes, but biological responses to receiving the placebo.

Scientists believe this is due to several factors, such as the conditioning effect, expectation effect, nocebo effect and the mind/body connection.

Rooted in classical conditioning, the conditioning effect causes participants to rely on verbal suggestions. For example, if a researcher tells a participant the treatment will relieve pain, the participant may report a lower pain level while only receiving the placebo.

The expectation effect is similar to the conditioning effect. When patients expect a result from a treatment, they may experience those outcomes even with the placebo. If a participant has an interest and mission to lose weight, for instance, they may begin to behave in a manner conducive to weight loss while taking the placebo. On the other hand, participants entering a clinical trial expecting side effects may begin to feel negative outcomes during the trial.

Although the placebo does not cause any reactions to a person, participants have reported a phenomenon known as the nocebo effect. Patients claim that the placebo caused illness and distress during the experimental trial. In one study, researchers told they were inhaling irritants and allergens during the trial, but given water vapor as the placebo. 48 percent of the 40 participants experienced negative outcomes in the forms of increased airway resistance and asthmatic attacks.

The mind-body connection can be very powerful with physical and psychological responses. Personality factors also play a role in the placebo effect. Participants with personality traits towards reward-seeking, altruism, optimism, empathy and spirituality behaviors may show a response with a placebo.

The Advantages and Disadvantages of Using Placebos

The drawbacks to using a placebo-controlled group during a clinical trial include participants dropping out during the study, biased patient reporting and the timing of natural healing.

Although there are disadvantages to using placebos, the placebo effect in many instances improves outcomes for participants, such as remembered wellness. Patients may remember their life before they were ill and improve their condition over time without the treatment. Participants taking a placebo may also change their behaviors resulting in healthier lifestyles and habits.

What the Results Mean

When using placebo-controlled groups during a clinical trial, researchers must be able to differentiate between the placebo and the trial drug or experimental treatment. One study concluded that placebo response rates and medication response rates during clinical trials have a mutual relationship with the placebo showing lower healing rates for nervous diseases, substance abuse and neoplasms.

With both the placebo-controlled group and the treatment group believing they are receiving the experimental drug, researchers are able to collect and analyze their results. Using this method, researchers can confirm if the new treatment has any effects beyond the placebo.

What You Should Know Before a Clinical Trial

If you are considering a clinical trial for a condition, ask the researchers about their use of placebos in the control group. The facility or institution holding the experimental trial should have you sign a consent document that informs participants about the chance of taking a placebo instead of the actual treatment.

Placebo-controlled experimental trials can advance medical treatments when executed properly. Ask questions about the study design and stay informed throughout the clinical trial. It is important that you understand the risks and obligations of the clinical trial as well as hold the institution to medical and research ethics guidelines.

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