[The early history of the Danish twin registry].

The Danish Twin Registry was initiated at the Copenhagen University Institute for Human Genetics in 1954 by professor Tage Kemp and his assistants, Bent Harvald and Mogens Hauge. The project was until 1960 primarily financed by US National Cancer Institutes. Twin pairs both of same and different sex, born 1870-1910 were drawn from the birth registers and followed-up through the national registers until death or present place of living. Later on same sex pairs born 1911-30 were added. Besided cancer a multitude of other disorders were registered. Intensive studies on identical twins grown up apart were undertaken by Niels Juel-Nielsen, on criminal behaviour by Karl O. Christiansen, on smoking habits by Elisabeth Raaschou-Nielsen, on peptic ulcer by Kaj Gotlieb Jensen, on schizophrenia by Margit Fischer. Among early remarkable results should be mentioned the modest influence of genetic versus environmental factors in most cases of cancer, the strong genetic impact in mental and moral qualities, the approximate genetic/environmental ratio of 50/50 for the orgin of criminal behaviour and a corresponding ratio of 25/75 for life expectancy. In 1971 the Danish Twin Registry was moved to Odense Universty.