Causal association factors can be revealed by

Case-control studies often retrospective studies are a common first approach to test the causal hypothesis. In recent years case-control study has emerged as a permanent method of epidemiological investigation. - Both exposure and outcome have occurred before the study. - The study proceeds backward from effect to cause. - It uses a control or comparison group to suppo or refute an inference Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 79