[Swedish twin study surveys how antisocial behavior is developed. Hereditary factors are more important in girls, in older children and in aggressive behavior].

During the 20th century, political opinions and scientific theories rather than scientific results have incited swings in public discourse concerning the origin of criminal and other behaviors. Twin-studies, adoption-studies and animal studies have shown that both genes and environmental factors are important. A longitudinal study of all twins in Sweden born between May 1985 and December 1986 has been initiated to examine how genes and environmental factors influence the development of, inter alia, antisocial behavior. The study has shown that genetic factors in antisocial behavior are more important in girls, in aggressive behavior, and in older children. Further, genes and environmental factors of importance in childhood were important also in early adolescence.