Genes and environment in the inheritance of morbidity and mortality.

During the past 30 years, the Danish Adoption Registry has been used in the analysis of the effect of genes and family environment on the development of mental disorders. During the last 15 years, the registry has also been used for similar analyses of somatic disorders, including obesity and premature death from somatic disorders. This article discusses the potential problems generally related to inference on morbidity from mortality data and particularly when using mortality data in adoption studies. We conclude that further insight into the question of nature, nurture or both requires extending the studies to include morbidity data as well as mortality data. We suggest that expanding the study by including biological and adoptive siblings and by using recently developed statistical methods will considerably strengthen the adoption study of morbidity and mortality.