October 18, 2016

Understanding Clinical Studies

Part of the challenge of explaining clinical research to the public is describing the important points of a study without going into a detailed account of the study鈥檚 design. There are many different kinds of clinical studies, each with their own strengths and weaknesses, and no real shorthand way to explain them. Researchers sometimes don鈥檛 explicitly state the kind of study they鈥檙e talking about. To them, it鈥檚 obvious; they鈥檝e been living and breathing this research for years, sometimes decades. But study design can often be difficult even for seasoned health and science communicators to understand.

The gold standard for proving that a treatment or medical approach works is a well-designed randomized controlled trial. This type of study allows researchers to test medical interventions by randomly assigning participants to treatment or control groups. The results can help determine if there鈥檚 a cause-and-effect relationship between the treatment and outcomes. But clinical researchers can鈥檛 always use this approach. For example, scientists can鈥檛 ethically study risky behaviors by asking people to start smoking or eating an unhealthy diet. And they can鈥檛 study the health effects of the environment by assigning people to live in different places.

Thus, researchers must often turn to some type of observational study, in which a population鈥檚 health or behaviors are observed and analyzed. These studies can鈥檛 prove cause and effect, but they can be useful for finding associations. Observational studies can also help researchers understand a situation and come up with hypotheses that can then be put to the test in clinical trials. These types of studies have been essential to understanding the genetic, infectious, environmental, and behavioral causes of disease.

We鈥檝e developed a one-page guide to clarify the different kinds of clinical studies researchers use, to explain why researchers might use them, and to touch a little on each type鈥檚 strengths and weaknesses. We hope it can serve as a useful resource to explain clinical research, whether you鈥檙e describing the results of a study to the public or the design of a trial to a potential participant. Please take a look and share your thoughts with us by sending an email to sciencehealthandpublictrust@mail.nih.gov.