Types of Epidemiological Study

Not meant to be exhaustive.

Cross-Sectional Studies

Slice in time. There is no temporality in cross-sectional studies. It's a slice in time. Because of this, there cannot be causal assertions. You can only speak of associations.

Cohort Studies

Prospective: Study begins at point of exposure. You have a lot of control. You cannot always assume causality. Kinda costly for rare outcomes (gotta recruit a lot of people!)

Retrospective: Study begins at point of outcome. No control (lol). Inexpensive (already happened, someone else paid the bill). But you're limited in terms of sampling and quality (already happened). And you cannot always assume causality.

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Cohort studies can start with cross-sectional studies where you can establish prevalence.

Case-Control Studies

These can only be retrospective. You can study just one outcome. Big challenge is bias: you recruit your cases separately from controls (you can match, for example, to get over this problem).