Vol. 7, No. 4, 2001 Page 4
A study of teenaged twins indicates that behavioral disinhibition is highly heritable, and may underlie the often-seen association of attention deficit hyperactivity disorder (ADHD), conduct disorder (CD), early experimentation with drugs and alcohol, and novelty-seeking behavior.
Susan Young and colleagues studied 172 monozygotic (identical) and 162 dizygotic (fraternal) twin pairs, using psychiatric interviews and personality assessments. The researchers found significant associations among ADHD, CD, novelty-seeking, and early drug use. Young et al. say their data suggest that a single vulnerability, behavioral disinhibition, may account for the frequent co-occurrence of these problems. They estimate the heritability of this trait at .84, which they note is "markedly higher than the heritabilities for the individual measures."
The common factor among childhood behavior problems, the researchers conclude, "may be the inability to inhibit behavior, despite its social undesirability and cascade of familial, educational, psychological, and possible legal consequences." (see related articles, Crime Times, 2001, Vol. 7, No. 4, Page 1 and Crime Times, 2001, Vol. 7, No. 4, Page 5.)
"Genetic and environmental influences on behavioral disinhibition," Susan E. Young, Michael C. Stallings, Robin P. Corley, Kenneth S. Krauter, and John K. Hewitt, American Journal of Medical Genetics, Vol. 96, 2000, 684-95. Address: Susan E. Young, Institute for Behavioral Genetics, Campus Box 447, University of Colorado, Boulder, CO 80309.