Understanding and Preventing Violence, Volume 2: Biobehavioral Influences (1994)
Chapter: Iowa Adoption Studies: Cadoret
sample was consistent with gene-environment interaction, although the interaction term is not significant (Cloninger et al., 1982).
At the same time, the Swedish results demonstrate that the genetics of violence cannot be divorced from the study of alcohol abuse (and, in U.S. society today, probably other substance abuse as well). There may be important genetic differences among individuals who commit serious offenses as a function of liability toward alcohol and drug abuse.
Iowa Adoption Studies: Crowe
By checking penal institution records in Iowa, Crowe (1972) identified 41 female offenders (90% of whom were felons) who gave up a total of 52 children for adoption. A consecutive series of control adoptees was identified through state records and matched on age, sex, race, and approximate time of adoption. At an average age of 25 (range from 15 through 45), the adoptees were traced through Iowa arrest records. The adopted offspring of the female felons were more likely to have had an arrest record (15%) and conviction (14%) than the control adoptees (4% and 2%, respectively). Five of the 52 probands were incarcerated in Iowa for an offense, compared to none of the controls (Crowe, 1972). Personal follow-up on 70 percent of the sample revealed that 13 percent of probands met diagnostic criteria for antisocial personality, whereas only one control (2%) was diagnosed as a probable antisocial personality (Crowe, 1974). Several placement variables (age at placement and length of time in temporary care before adoption) predicted antisocial outcomes.
Iowa Adoption Studies: Cadoret
Cadoret continued his previous line of adoption research by identifying a series of adopted children from Iowa adoption records whose biological parents had some recorded psychopathology. (This sample did not overlap with that of Crowe.) A second, matched group of adoptees whose record data did not mention psychopathology in the biological parents served as controls. Both groups were personally followed up between the ages of 10 and 37. Sample attrition was high among the adoptive families—more than 30 percent of those contacted refused to participate (Cadoret, 1978).
Sample sizes became small when adoptees were grouped by age and by diagnosis of biological parents—only nine male and three female adult adoptees had a biological parent with a diagnosis
