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Br J Psychiatry. 2001 Sep;179:224-9.

Examining the comorbidity of ADHD-related behaviours and conduct problems using a twin study design.

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1
Child and Adolescent Psychiatry Section, Department of Psychological Medicine, University of Wales College of Medicine, Cardiff, UK.

Abstract

BACKGROUND:

Although attention-deficit hyperactivity disorder (ADHD) and conduct disorder (CD) frequently co-occur, the underlying mechanisms for this comorbidity are not well understood.

AIMS:

To examine whether ADHD and conduct problems share common risk factors and whether ADHD+CD is a more heritable variant of ADHD.

METHOD:

Questionnaires were sent to 2846 families. Parent-rated data were obtained for 2082 twin pairs and analysed using bivariate genetic analysis and a liability threshold model approach.

RESULTS:

The overlap of ADHD and conduct problems was explained by common genetic and non-shared environmental factors influencing both categories. Nevertheless, the two categories appeared to be partly distinct in that additional environmental factors influenced conduct problems. It appeared that ADHD+CD was a genetically more severe variant of ADHD.

CONCLUSIONS:

Conduct problems and ADHD share a common genetic aetiology; ADHD+CD appears to be a more severe subtype in terms of genetic loading as well as clinical severity.

PMID:
11532799
[Indexed for MEDLINE]
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