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Phenotypic subtypes in attention deficit hyperactivity disorder in an isolated population
Esther A Croes1, Rachid El Galta, Jeanine J Houwing-Duistermaat
1Genetic Epidemiology Unit, Department of Epidemiology and Biostatistics, Erasmus Medical Centre, PO Box 1738, 3000 DR Rotterdam, The Netherlands.
European Journal of Epidemiology
|September 20, 2005
Summary
Using two informants in diagnosing Attention Deficit Hyperactivity Disorder (ADHD) identifies a phenotype with a strong genetic component. The inattentive ADHD subtype shows significant familial clustering, suggesting a potential recessive genetic origin.
Area of Science:
- Genetics
- Psychiatry
- Population Studies
Background:
- Attention Deficit Hyperactivity Disorder (ADHD) is a complex neurodevelopmental disorder with suspected genetic underpinnings.
- Familial aggregation studies are crucial for understanding the genetic architecture of ADHD.
- Phenotypic heterogeneity in ADHD may reflect distinct genetic etiologies.
Purpose of the Study:
- To investigate the impact of using two informants (parents and teachers) on identifying ADHD phenotypes with stronger genetic components.
- To compare the familial aggregation patterns across the three ADHD phenotypic subtypes (inattentive, hyperactive/impulsive, combined).
- To explore potential genetic origins, including recessive inheritance, for the inattentive ADHD subtype.
Main Methods:
- Diagnosis of lifetime ADHD in a Dutch isolated population using parent and teacher reports.
- Creation of subgroups based on the number of informants (one vs. two).
- Calculation of mean kinship coefficients and genealogical analysis to assess genetic relatedness within phenotypic subtypes.
Main Results:
- Patients diagnosed with two informants exhibited a significantly higher mean kinship coefficient than those with one informant (p = 0.03).
- The inattentive ADHD subtype showed significantly higher relatedness to a common ancestor (p = 0.03) and a higher prevalence of consanguineous marriages (81%) than expected.
- Patients with the inattentive phenotype were more closely related (p<0.01) compared to other ADHD phenotypes.
Conclusions:
- Employing two informants in ADHD diagnosis enhances the identification of phenotypes with substantial genetic influence.
- The inattentive ADHD subtype demonstrates strong familial clustering and suggests a possible recessive genetic etiology.
- Genetic studies of ADHD should consider informant methodology and phenotypic specificity to elucidate underlying genetic factors.