Cohort studies differ from clinical trials in that no intervention, treatment, or exposure is administered to participants in a cohort design; and no control group is defined. Rather, cohort studies are largely about the life histories of segments of populations and the individual people who constitute these segments.

Can a cohort study have an intervention?

A cohort study is an observational analytical study. It does NOT include intervention.

How is an intervention study different from a cohort study?

The basic difference is that in the interventional study, it is the investigators who assign each person to take or not to take aspirin, whereas in the cohort study, this is determined by an extraneous factor.