title: Genetic and environmental influences on the familial transmission of externalizing disorders in adoptive and twin offspring.
abstract: OBJECTIVE
  Twin-family studies have shown that parent-child resemblance on substance use disorders and antisocial behavior can be accounted for by the transmission of a general liability to a spectrum of externalizing disorders. Most studies, however, include only biological parents and offspring, which confound genetic and environmental transmission effects.
  
  
  OBJECTIVE
  To examine the familial transmission of externalizing disorders among both adoptive (genetically unrelated) and biological relatives to better distinguish genetic and environmental mechanisms of transmission.
  
  
  METHODS
  Family study design wherein each family included the mother, father, and 2 offspring, including monozygotic twin, dizygotic twin, nontwin biological, and adoptive offspring. Structural equation modeling was used to estimate familial transmission effects and their genetic and environmental influences.
  
  
  METHODS
  Participants were recruited from the community and assessed at a university laboratory.
  
  
  METHODS
  A total of 1590 families with biological offspring and 409 families with adoptive offspring. Offspring participants were young adults (mean age, 26.2 years).
  
  
  METHODS
  Symptom counts of conduct disorder, adult antisocial behavior, and alcohol, nicotine, and drug dependence. RESULTS There was a medium effect for the transmission of the general externalizing liability for biological parents (r = 0.27-0.30) but not for adoptive parents (r = 0.03-0.07). In contrast, adoptive siblings exhibited significant similarity on the general externalizing liability (r = 0.21). Biometric analyses revealed that the general externalizing liability was highly heritable (a2 = 0.61) but also exhibited significant shared environmental influences (c2 = 0.20).
  
  
  CONCLUSIONS
  Parent-child resemblance for substance use disorders and antisocial behavior is primarily due to the genetic transmission of a general liability to a spectrum of externalizing disorders. Including adoptive siblings revealed a greater role of shared environmental influences on the general externalizing liability than previously detected in twin studies and indicates that sibling rather than parent-child similarity indexes important environmental risk factors for externalizing disorders.
authors: Department of Psychiatry, University of Michigan, Ann Arbor.
authors: Brian M
authors: BM
authors: Hicks
authors: Katherine T
authors: KT
authors: Foster
authors: William G
authors: WG
authors: Iacono
authors: Matt
authors: M
authors: McGue
mesh_terms: D000293:Adolescent; D000328:Adult; D000987:Antisocial Personality Disorder / Q000235:genetics; D019955:Conduct Disorder / Q000235:genetics; D004200:Diseases in Twins / Q000235:genetics* / Q000523:psychology*; D004777:Environment; D005192:Family Health; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010290:Parents; D012307:Risk Factors; D035781:Siblings / Q000523:psychology; D019966:Substance-Related Disorders / Q000235:genetics; D014429:Twins, Dizygotic / Q000235:genetics* / Q000523:psychology; D014430:Twins, Monozygotic / Q000235:genetics / Q000523:psychology
references: Arch Gen Psychiatry. 1999 Oct;56(10):921-6
references: 10530634
references: Arch Gen Psychiatry. 1998 Nov;55(11):973-9
references: 9819065
references: J Adolesc. 2001 Oct;24(5):579-96
references: 11676506
references: Behav Genet. 1984 Jul;14(4):325-43
references: 6542356
references: Arch Gen Psychiatry. 2007 May;64(5):566-76
references: 17485608
references: Arch Gen Psychiatry. 1998 Nov;55(11):982-8
references: 9819066
references: Arch Gen Psychiatry. 2009 Jun;66(6):640-8
references: 19487629
references: Arch Gen Psychiatry. 2002 Dec;59(12):1125-32
references: 12470129
references: Nat Genet. 2010 May;42(5):441-7
references: 20418890
references: Behav Genet. 2007 May;37(3):449-62
references: 17279339
references: Am J Psychiatry. 2010 Sep;167(9):1066-74
references: 20634367
references: J Stud Alcohol. 1996 Jan;57(1):8-18
references: 8747496
references: Am J Med Genet. 1999 Aug 20;88(4):391-7
references: 10402507
references: Arch Gen Psychiatry. 2003 Sep;60(9):929-37
references: 12963675
references: Behav Genet. 2006 Jul;36(4):603-15
references: 16619135
references: Psychol Med. 1997 Nov;27(6):1381-96
references: 9403910
references: Behav Genet. 2006 Jul;36(4):591-602
references: 16557361
references: J Abnorm Psychol. 2007 Aug;116(3):433-47
references: 17696699
references: Dev Psychopathol. 1999 Fall;11(4):869-900
references: 10624730
references: J Abnorm Psychol. 2002 Aug;111(3):411-24
references: 12150417
references: J Stud Alcohol. 1987 Jan;48(1):1-8
references: 3821113
references: Arch Gen Psychiatry. 2004 Sep;61(9):922-8
references: 15351771
references: Behav Genet. 2011 Jul;41(4):459-75
references: 21153693
references: Arch Gen Psychiatry. 2003 Jul;60(7):709-17
references: 12860775
references: Am J Med Genet. 2000 Oct 9;96(5):684-95
references: 11054778
references: Behav Genet. 2010 May;40(3):377-93
references: 20013306
references: J Abnorm Psychol. 1998 Aug;107(3):363-74
references: 9715572
references: Arch Gen Psychiatry. 1986 Dec;43(12):1131-6
references: 3778110
references: Arch Gen Psychiatry. 2007 Jul;64(7):830-42
references: 17606817
references: Arch Gen Psychiatry. 1985 Feb;42(2):161-7
references: 3977542