What is a main limitation of cross-sectional studies?

• A. It requires long follow-up
• B. It cannot infer causality or temporality
• C. It uses randomized assignment
• D. It is highly expensive

Answer: (B)

Cross-sectional studies capture exposure and outcome at a single point in time, like taking a snapshot of a population. The main limitation is that because both are measured simultaneously, you can’t determine which came first. Without knowing temporality, you can’t infer causality—the observed association could be due to reverse causation or to another factor influencing both exposure and outcome. This design is still useful for estimating prevalence and generating hypotheses, but it can’t prove cause-and-effect relationships.

The other statements don’t fit as the defining limitation: requiring long follow-up is a hallmark of longitudinal or cohort studies; randomized assignment is a feature of experimental designs; and while cost can vary, it isn’t the fundamental constraint of this approach.