Genetic and environmental influences on juvenile antisocial behaviour assessed on two occasions

Background. There is conflicting evidence concerning the magnitude of genet ic and shared environmental influences on juvenile antisocial behaviour (AB ). The use of more than one assessment of AB may yield more accurate estima tes of these influences. Methods. Retrospective reports of antisocial behaviour prior to age 18 were obtained on two occasions from a population-based sample of 3522 adult mal es from male-male twin pairs: phone interviews (wave 1) and self-report que stionnaires obtained 19 months later (wave 2). Structural equation modellin g estimated the genetic and environmental influences on reliably-measured A B. Factors related to participation of co-twin at wave 1, attrition between waves 1 and 2, and reliability of wave 1 and wave 2 assessments were also investigated. Results. Twin analyses revealed that genetic, shared environmental, and non -shared environmental influences accounted for approximately 33 % (95 % Cl = 9-57 %), 31 % (95 % Cl = 10-51 %) and 36 % (95 % CI = 29-44 %) of the Var iance of reliably measured AB, respectively. We also found significant occa sion-specific genetic influences on wave 1 AB. Wave 1 AB did not predict wa ve 1 participation of co-twin or attrition, but was related to reliability. Go-twins of MZ twins and younger twins were more likely to participate at wave 1; attrition was predicted by being a DZ twin, lack of initial partici pation of co-twin, fewer years of education, and fewer children. Being olde r, being unmarried, and having less psychopathology were associated with gr eater reliability. Conclusions. When measurement error is taken into account, both genetic and shared environmental factors are significant influences on juvenile AB, ac counting for approximately one-third of variation. The origin of the specif ic genetic influences on wave 1 AB is unclear, but may be due to factors re lated to measurement.