How does recall bias affect the results of a retrospective cohort study?

Retrospective cohort studies are at high risk for research biases like recall bias. Whenever individuals are asked to recall past events or exposures, recall bias can occur. This is because individuals with a certain disease or health outcome of interest are more likely to remember and/or report past exposures differently to individuals without that outcome. This can result in an overestimation or underestimation of the true relationship between variables and affect your research.