Sex differences in the etiology of aggressive and nonaggressive antisocial behavior: Results from two twin studies
ABSTRACT Recent theory and results from twin and adoption studies of children and adolescents suggest greater genetic influence on aggressive as compared to nonaggressive antisocial behavior. In addition, quantitative or qualitative differences in the etiology of these behaviors in males and females have been indicated in the literature. The Child Behavior Checklist was completed by the parents of 1022 Swedish twin pairs aged 7-9 years and of 501 British twin pairs aged 8-16 years. Genetic factors influenced aggressive antisocial behavior to a far greater extent than nonaggressive antisocial behavior, which was also significantly influenced by the shared environment. There was a significant sex difference in the etiology of nonaggressive antisocial behavior. Bivariate analyses supported the conclusion that the etiologies of aggressive and nonaggressive antisocial behavior differ for males and females.
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ABSTRACT: The equal environments assumption (EEA) of the twin method posits that environmental influences that are etiologically relevant to a given phenotype are no more likely to be shared by monozygotic (MZ) than dizygotic (DZ) twin pairs. One method of testing the EEA is to evaluate whether increased rearing environment similarity in MZ twin pairs compared to DZ twin pairs is related to increased phenotypic correlation. In a sample of 885 twin pairs, we contrasted similarity in rearing environment between MZ and DZ twin pairs, examined the correlation between similarity in rearing environment and conduct disorder (CD), oppositional-defiant disorder (ODD), inattention, and hyperactivity-impulsivity symptom dimensions, and tested the effects of differential similarity in rearing environments between MZ and DZ twin pairs by testing whether rearing environment similarity moderated the correlations for the externalizing symptom dimensions. We found that MZ twins experienced substantially more similar rearing environments than DZ twins, but that there was little evidence that MZ and DZ correlations for the externalizing symptom dimensions varied by rearing environment similarity. Thus, these results constitute evidence for the validity of the EEA for childhood externalizing disorders.Behavior Genetics 10/2014; DOI:10.1007/s10519-014-9685-3 · 2.84 Impact Factor
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ABSTRACT: Background: Most research on violent perpetrators is based on male samples. Aims: To compare girls and boys admitted to an adolescent forensic unit due to physically violent and/or sexually coercive behavior. Methods: On an adolescent forensic ward, demographics, family, treatment, crime and victimization histories, diagnose, psychiatric symptoms and violent behaviors during care of all adolescents are collected in a cumulative database. These were compared between girls and boys admitted due to violent behaviors. Results: Girls were more often diagnosed with schizophrenia group psychoses. The symptom profiles and violence risk ratings did not differ by sex. The girls were less antisocial in general. They were more suicidal and displayed more promiscuous behaviors, and they had more commonly been victims of sexual abuse. During inpatient care they displayed much more often violent and uncontrollable behaviors than the boys. Conclusion: Treatment approaches that respond to the special needs of aggressive girls are required.Journal of Forensic Psychiatry and Psychology 08/2014; 25(6):636-657. DOI:10.1080/14789949.2014.943795 · 0.88 Impact Factor