The most common types of research studies involving people are separated into intervention and non-intervention studies. Intervention research studies often include using new drugs, devices, or treatments in clinical trials. Non-intervention research studies observe participants' behaviors and medical information.
Intervention-Based Research Studies
The purpose of an intervention-based research study is to evaluate new treatments and their effects on people. An intervention-based research study is conducted to determine the safety and/or effectiveness of experimental drugs, devices, treatment regimens, or preventive measures in people. These studies are very important for determining which treatments are best for individual patients.
Randomized Clinical Trials
A randomized clinical trial is an intervention-based research study where each participant has an equal chance of receiving the new treatment or something other than the new treatment. If a person does not receive the new treatment, they may be given a pill without active medication called a placebo (often a sugar pill) if there is no known therapy or standard proven therapy.
The participants who receive the new treatment are referred to as the treatment group and the participants who receive the placebo or standard care are referred to as the control group. The group to which any individual participant is assigned occurs randomly. When there are an equal number of participants in each clinical trial group it makes the comparison between the groups as accurate as possible. Because the results from a randomized clinical trial are so accurate, it is often considered the best way to learn whether a certain treatment works or not.
When participants do not know what treatment they are assigned to, the clinical trial is blinded. Double-blind clinical trials occur when both the participants and the doctors who treat them do not know whether they have been assigned to the control group or treatment group. Blinded trials are also referred to as masked trials.
It is important to keep in mind that when human research is conducted, professional investigators are obliged to adhere to the highest ethical principles.
Non-intervention Research Studies
Research studies that do not influence or change the behavior of the participants are considered non-intervention research studies.
- Observational research studies are non-intervention studies that determine how often a disease occurs in the study population, what the risk factors for a disease may be, or what the outcome of contracting a disease may be.
- Behavioral research studies are non-intervention studies where neuropsychological testing and questionnaires are often completed by participants.
Examples of non-intervention studies include large population-based epidemiology studies examining the frequency of a particular health problem, MRI studies, and genetic studies requiring a blood draw for genetic analysis.