What is the difference between a cross sectional study and a longitudinal study?

In a cross-sectional study, researchers collect data from individuals at a single point in time.

In a longitudinal study, researchers collect data from individuals repeatedly or continuously over an extended period of time (often years).

Cross-sectional studies are faster and less expensive to conduct than longitudinal studies. However, because they collect data at a single point in time, cross-sectional studies are not the best option for establishing cause-and-effect relationships.

A common practice is to conduct a cross-sectional study to generate hypotheses. You can then use this information to design a longitudinal study.