title: The etiologic role of genetic and environmental factors in criminal behavior as determined from full- and half-sibling pairs: an evaluation of the validity of the twin method.
abstract: BACKGROUND
  Twin studies have shown that criminal behavior (CB) is influenced by both genetic and shared environmental factors. Could these results be replicated using full-siblings and half-siblings?
  
  
  METHODS
  In 911 009 full-siblings reared together (FSRT), 41 872 half-siblings reared together (HSRT) and 52 590 half-siblings reared apart (HSRA), CB was assessed from the Swedish Crime Register. Modeling, including testing for age differences and rearing status, was performed using the OpenMx package.
  
  
  RESULTS
  Five sibling models were fitted examining FSRT and HSRT 0-2 years different in age, and both FSRT and HSRT, and FSRT, HSRT and HSRA 0-10 years different in age with and without a specified shared environment indexing age differences. Heritability estimates for CB ranged from 33 to 55% in females and 39 to 56% in males, similar to those found in our prior twin study on the same population. Estimates for the shared environment varied from 1 to 14% in females and 10 to 23% in males, lower than those estimated in the twin study. The specified shared environment indexed by sibling age differences was significant in all models tested.
  
  
  CONCLUSIONS
  Heritability estimates for CB from full- and half-siblings closely approximated those found from twins in the same population, validating the twin method. Shared environmental estimates were lower, suggesting the presence of shared environmental factors for CB specific to twins. When rearing status can be assessed, full- and half-siblings offer an additional method for assessing the role of genetic and environmental factors in complex disorders. However, age differences in siblings may need to be included in the models.
authors.affiliation: Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University,Richmond,VA,USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Kendler
authors.affiliation: Center for Primary Health Care Research,Lund University,Malmö,Sweden.
authors.forename: S L
authors.initials: SL
authors.lastname: Lönn
authors.affiliation: Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University,Richmond,VA,USA.
authors.forename: H H
authors.initials: HH
authors.lastname: Maes
authors.affiliation: Center for Primary Health Care Research,Lund University,Malmö,Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Sundquist
authors.affiliation: Center for Primary Health Care Research,Lund University,Malmö,Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Sundquist
mesh_terms: D000293:Adolescent; D000328:Adult; D003415:Crime; D000066479:Criminal Behavior; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D012042:Registries; D012307:Risk Factors; D035781:Siblings; D012931:Social Environment; D013548:Sweden; D055815:Young Adult
keywords: Crime; Sweden; half-siblings; heritability; shared environment; siblings; twin modeling