Epi Night School Lesson 6: Correlation vs. Causation

When two things look related, but may or may not be.

Welcome back to Epidemiology Night School! So far, we’ve learned how to describe health problems, measure disease with incidence and prevalence, and dig deeper into why things happen with analytic tools like case-control and cohort studies. Today, we’re tackling one of the trickiest concepts in epidemiology (and in life): correlation vs. causation.

If you’ve ever heard someone say, “People who drink more coffee live longer!” or “E-cigarettes cause kids to smoke!”, you’ve encountered the messy line between two things that look related (correlation) and two things where one actually causes the other (causation). Confusing these ideas can lead to bad science, bad decisions, and some hilarious headlines.

So, let’s break it down, sprinkle in some real-world examples, and learn to spot the difference between “coincidence” and “cause.”