The beauty, logic and limitations of twin studies

During the last fifty years more than 2700 twin studies have been published, examining the etiology of ahigh number of traits. Twin studies enable investigation of both genetic and environmental effects, andthereby also examination of causal factors involved in human traits and disorders. The beauty of twinstudies resides in the potential of studying the unobserved by the logic of a design. The aim of this article isto outline central...