7.2 Study designs for etiology and risk

Commonly, epidemiological or observational studies are utilized to investigate etiology and risk. Observational studies aid in studying causal associations between an exposure and disease/health outcome (for example associations between occupational risk factors and lung cancer, or the adverse effects of a treatment in healthcare), although distinguishing true causality generally requires experimental research. Observational studies do not involve manipulation on the part of the researcher. These studies rely on the natural or “ecological” events of exposures and disease, where the researcher simply observes certain characteristics of the sample population as they occur “naturally”, and records the relevant data (The Joanna Briggs Institute b 2014). In this way they can be distinguished from experimental or quasi-experimental studies (such as RCTs and controlled clinical trials) where there is researcher manipulation of the independent variable (the potential cause or the exposure) (The Joanna Briggs Institute b 2014).