Research In Brief: Controlled Studies

In 2016, we began the Research In Focus series, highlighting new and interesting findings from NIDILRR-funded studies, presented in a reader-friendly format. As a follow up, we offer our occasional series Research In Brief, where we break down some of the terms you might find in peer-reviewed studies.

In this month’s Research in Brief, we explore terms related to controlled studies. Controlled studies are used to test the impact of a new program, drug, device, or other intervention on people’s health or quality of life by comparing groups of people who do vs. do not receive the new intervention.

A randomized controlled trial (RCT) is a study in which participants are randomly divided into “experimental” and “control” groups. The participants are assigned to a group based on the random flip of a coin, or a random number, so that the groups will be as similar as possible before the study. Then, the participants in the experimental group receive the new intervention, while the participants in the control group receive something different. For example:

  • In a “placebo-controlled” study, the control group might receive something that looks like the intervention, but is not; for example, they might receive sugar pills instead of the experimental drug. Thus, the participants in both groups will not know which group they are in. A “double-blind” study is a placebo-controlled study where the participants and the researchers do not know which group the participant is in; this information is only tracked on a computer. In a “single-blind” study, the researchers know which groups the participants are in, but the participants do not.
  • In a “waitlist-controlled” study, the experimental group receives the new intervention immediately, while the control group is offered the intervention after the study is over. While the control group participants are waiting for the intervention, they may receive “treatment as usual.” For example, if researchers want to test a new counseling program for college students, they might offer the program to the students in the experimental group immediately, while the students in the control group may have access to the regular counseling resources at their college.
  • In an “active-controlled” study, the experimental group might receive a new intervention, while the control group receives an already-accepted intervention. For example, if researchers want to compare a new antidepressant drug to Prozac, they might give the new drug to the experimental group participants and Prozac to the control group participants, and look at differences between the two groups at the end of the study.

Sometimes, it’s not possible to do a randomized controlled study. For example, if a new program is happening at one school but not another, it may not be possible to randomly assign people to the new program. In these kinds of cases, researchers might compare outcomes between people who are attending schools with the new program vs. those attending other schools without the program.

To learn more about controlled studies conducted by NIDILRR-funded grantees, check out these Research In Focus articles:

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