Letters to the Editor Do we need more twin studies? The Healthy Twin Study, Korea

nological progress have made the analysis of individual genetic variation much more feasible. However, genetic variations responsible for common complex human diseases and traits are largely unknown, with a few exceptions of specific subtype of common diseases (e.g. early onset type diabetes or Alzheimer disease). 1 Twin study has evolved from the classical twin study design, in which comparison of concordance in traits or diseases between monozygotic and dizygotic twins provided evidence about the genetic and environmental contributions to the phenotypes/diseases of interest. 2 Current twin studies in Europe, Australia, and other countries are already comprehen