Antisocial behavior and substance dependence disorders exact a heavy
financial and human cost on society. A better understanding of the mechanisms
of familial transmission for these "externalizing" disorders is necessary
to better understand their etiology and to help develop intervention strategies.
To determine the extent to which the family transmission of externalizing
disorders is due to a general vs a disorder-specific vulnerability and, owing
to the genetically informative nature of our data, to estimate the heritable
vs environmental nature of these transmission effects.
We used structural equation modeling to simultaneously estimate the
general and specific transmission effects of 4 externalizing disorders: conduct
disorder, adult antisocial behavior, alcohol dependence, and drug dependence.
Participants were recruited from the community and were interviewed
in a university laboratory.
The sample consisted of 542 families participating in the Minnesota
Twin Family Study. All families included 17-year-old twins and their biological
mother and father.
Main Outcome Measures
Symptom counts of conduct disorder, the adult criteria for antisocial
personality disorder, alcohol dependence, and drug dependence.
Transmission of a general vulnerability to all the externalizing disorders
accounted for most familial resemblance. This general vulnerability was highly
heritable (h2 = 0.80). Disorder-specific
vulnerabilities were also detected for conduct disorder, alcohol dependence,
and drug dependence.
The mechanism underlying the familial transmission of externalizing
disorders is primarily a highly heritable general vulnerability. This general
vulnerability or common risk factor should be the focus of research regarding
the etiology and treatment of externalizing disorders.