‘Mendelian randomization’ equals instrumental variable analysis with genetic instruments

Interest in instrumental variable (IV) analyses using genetic instruments has been growing over the past 4 years. The background, strength and weaknesses of this approach, which in the epidemiology literature has been referred to as 'Mendelian randomization', has been recently reviewed by Lawlor et al. (Statist. Med. 2007. DOI: 10.1002/sim.3034). We suggest a change in the nomenclature of 'Mendelian randomization' and discuss issues relevant to IV analysis including instrument validation, motivation of IV analysis and interpretation of IV estimates in order to motivate a more consistent and standard use of IV analysis across applications using genetic instruments.