'Mendelian randomization': an approach for exploring causal relations in epidemiology

Objectives: To assess the current status of Mendelian randomization (MR) approach in effectively influencing the observational epidemiology for examining causal relationships. Methods: Narrative review on studies related to principle, strengths, limitations, and achievements of MR approach. Results: Observational epidemiological studies have repeatedly produced several beneficiary associations which were discarded when tested by standard randomized controlled trials (RCTs). The technique which is more feasible, highly similar to RCTs, and has the potential to establish a causal relationship between modifiable exposures and disease outcomes is known as MR. The technique uses genetic variants related to modifiable traits/exposures as instruments for detecting causal and directional associations with outcomes. Conclusions: In the last decade, the approach of MR has methodologically developed and progressed to a stage of high acceptance among the epidemiologists and is gradually expanding the landscape of causal relationships in non-communicable chronic diseases. (C) 2016 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.