How is a "case-control study" defined?

A case-control study is defined as a design that compares individuals with a specific condition (the cases) to those without it (the controls). This approach is particularly valuable in epidemiological research and clinical psychology for understanding the factors that may contribute to the development of a condition or illness. By focusing on subjects who already have the condition, researchers can retrospectively identify risk factors, behaviors, or exposures that are more prevalent in the case group than in the control group. This comparison can help to build hypotheses about causation and inform future research directions.

The other options reflect different types of research designs: a single-subject longitudinal study, a prevalence survey, and qualitative interviews, none of which align with the definition or purpose of a case-control study. Instead, these methods serve distinct functions in research, contributing to knowledge in varied ways but not specifically comparing cases to controls as required in a case-control framework.