Cohort studies are a type of observational study that follows a group of individuals (cohort) over a period of time to study how certain factors are associated with outcomes of interest. These studies can be prospective or retrospective in nature and are particularly useful in investigating the causes and risk factors for diseases or health outcomes. Cohort studies can provide valuable information about the natural history of a disease, the effectiveness of interventions, and the impact of risk factors on health outcomes. They are often used in medical, epidemiological, and public health research to establish causal relationships between exposures and outcomes.