Case Control and Cohort Studies Posted on February 29, 2008 Bruce G. Link (bio) reviews the pros and cons of the two types of study.

The case control study is where you select people on the disease rather than on the risk factor. So you get people that have the disease, and then you get controls who are as similar as possible. And then you look for the risk factors, differences between the cases who have the disease and the controls who don't, retrospectively. You're asking back in time.

For rare disease it's a much cheaper study to undertake because you don't have to wait for the cases to develop. You go to a setting, and you can find the people who have the disease, have controls, and you can do the study quickly.

Cohort study, especially, you have to find people who have the risk factor and then follow them forward until they develop the disease. That's considered a better design. It has fewer biases. It's not perfect, but it has fewer biases.

Harder to do. You have to wait longer. It costs more. If it's a rare disease, not enough cases emerge.

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