An observational study is a type of investigation used in clinical research to simply observe a group of people or subjects without intervening or influencing them. It allows researchers to measure a particular outcome and look for relationships between them.
An observational study can be performed prospectively, which looks at a particular outcome going forward, or retrospectively, which looks at data already collected.
An observational study is different from an experimental study. In an experimental study, the researcher introduces an intervention, e.g., a drug. They investigate the effect of this on the participants in the study and note any differences.
There are two main types of observational studies:
- Cohort studies – a group of people without a disease are separated into two categories, those who are exposed to a potential cause of the disease and those who are not exposed. They are then observed over time to determine if any new disease cases develop.
- Case-control studies – two similar groups of people are observed. Those who have a particular disease and those who don’t. It then compares them to a certain exposure. This type of study attempts to link the effects of a disease to the cause.