What types of clinical research are there?

Two doctors looking at medical results on digital tablet in front of a hospital building.

Before any new therapy can be put on the market, it must be tested to ensure its safety and effectiveness, and the research for this process is done through clinical trials. Clinical trials evaluate new drugs, devices, packaging, and behaviors in order to determine if these potential therapies work for particular conditions or patient populations.

Clinical trials play a pivotal role in assessing the viability of new treatments. The extensive data gathered from these studies is then submitted to the Food and Drug Administration (FDA) as part of the approval process. Because this is a requirement for any new therapy, there are many types of medical research, which we will outline below.

The types of clinical trials

A clinical study involves research using human volunteers, with the intention to add to medical knowledge. Depending on what is being tested and the research question at hand, there are two broad categories that a clinical trial might fall into.

Interventional studies test whether a specific intervention (i.e. a new drug, device, or behavioral change) can impact health-related outcomes. In interventional studies, participants are divided into different groups and are assigned at random to receive the intervention. The group receiving the intervention will be compared against a group that receives a placebo or is given the current standard of care. Interventional trials are typically blinded, meaning the groups are not aware of which category they are in, and some trials are double-blinded, meaning neither the participants nor the researchers are aware of the distinction.

Observational studies assess health outcomes in groups of participants according to a research plan or protocol. Patients with the same disease or treatment plan are observed over a period of time, and researchers watch how participants respond to their treatments while taking relevant variables into account. A patient registry, commonly found on patient advocacy sites, is a type of observational study that collects information about patients' medical conditions and/or treatments to better understand how a condition or treatment affects patients in the real world.

Categories of medical studies

In addition to the two main types of clinical trials, there are a few categories of clinical research that are defined by the FDA. 

  • Treatment research generally involves an intervention.
  • Prevention research seeks better ways to keep disorders from developing or returning.
  • Diagnostic research looks for better ways to identify a particular disorder or condition. 
  • Screening research aims to find the best ways to detect certain disorders or health conditions. 
  • Quality of life research explores ways to improve comfort and quality of life for individuals with a chronic illness. 
  • Genetic studies aim to improve the prediction of disorders by identifying and understanding how genes and illnesses may be related.
  • Epidemiological studies seek to identify the patterns, causes, and control of health conditions in groups of people. 

Most clinical research programs are “outpatient,” meaning that participants do not stay overnight at the hospital. Some studies that require travel or more in-depth testing may be “inpatient,” meaning that participants will need to stay for at least one night in the hospital or research center.

FDA clinical trial phases

Before a potential new treatment reaches the public, it must go through the required phases of a clinical trial to be eligible for approval.

  • Phase I clinical trials: The first phase of human test trials tests solely for safety and typically enrolls approximately 20 to 100 healthy volunteers. This trial phase can last anywhere from several months to a year.
  • Phase II clinical trials: This phase tests for both safety and efficacy by utilizing participants that have the condition being studied. Trials in this stage can last from several months to a few years, and recruit up to several hundred patients with the condition to take part.
  • Phase III clinical trials: The largest phase of testing, Phase III trials enroll several hundred to several thousand volunteers. This testing phase can last several years as the FDA gathers thorough data about the drug's effectiveness and potential side effects.

How long are clinical trials?

Because there is so much research, data collection, and reporting involved with the study process, clinical trials typically take between six and seven years to complete. However, it is important to note that patients who choose to take part in a clinical trial will not have to be involved this long — generally, participants will be involved for a few months to a few years. For those interested in volunteering for a research study, the clinical team will be able to answer any questions about the duration of the trial as part of the informed consent process.

Volunteers play a critical role in the thorough evaluation of potential therapies for safety and efficacy. The rigorous testing conducted through clinical trials is essential for the approval and availability of new medications. Ready to participate in a study? Start your clinical trial search today: