The role of conduct disorder in explaining the comorbidity between alcohol and illicit drug dependence in adolescence.
BACKGROUND
Conduct disorder (CD), alcohol dependence (AD), and illicit drug dependence (IDD) frequently co-occur. This paper describes the result of an investigation of the extent to which comorbid alcohol and illicit drug dependence in adolescents are explained by etiological factors in common with conduct disorder.


METHODS
Participants were 645 MZ twin pairs, 702 DZ twin pairs, 429 biological sibling pairs, and 96 adoptive sibling pairs, aged 12-18 years, from a community based sample. Conduct disorder was measured using the Diagnostic Interview Schedule for Children-IV. Alcohol and illicit drug dependence were assessed using the Composite International Diagnostic Interview-Substance Abuse Module (CIDI-SAM). For each outcome, subjects were categorized into those with no symptoms, those with one or more symptoms but no diagnosis, and those with a diagnosis.


RESULTS
The heritability estimates for CD, AD, and IDD were 58, 66, and 36%, respectively. The genetic correlation between AD and IDD was partially explained by the genetic risk they both share with conduct disorder.


CONCLUSIONS
We conclude that conduct disorder in adolescents explains, in part, the co-occurrence of alcohol and illicit drug dependence. Specifically, the genetic contribution to their covariation is explained partially by the genetic contribution in common with conduct disorder.
Button
Tanya M M
TM
Institute for Behavioral Genetics, Campus Box 447, University of Colorado, Boulder, CO 80309, USA. tanya.button@colorado.edu
Rhee
Soo Hyun
SH
Hewitt
John K
JK
Young
Susan E
SE
Corley
Robin P
RP
Stallings
Michael C
MC
D000293:Adolescent; D000437:Alcoholism / Q000453:epidemiology*; D002648:Child; D015897:Comorbidity; D019955:Conduct Disorder / Q000453:epidemiology*; D005260:Female; D006801:Humans; D013287:Illicit Drugs; D008297:Male; D009293:Opioid-Related Disorders / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D014427:Twins
D013287:Illicit Drugs