ADHDgene Database

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Large-scale studies

Data Summary

Published Variant
- SNP: 1391
- CNV: 398
- Others: 173
Published Gene: 359
Published Region: 128
Pathway by PBA: 8
Study: 361

Study Report

Basic Info

Reference	Inkster B, 200415167700
Citation	Inkster B., Muglia P., Jain U. and Kennedy J. L. (2004) "Linkage disequilibrium analysis of the dopamine beta-hydroxylase gene in persistent attention deficit hyperactivity disorder." Psychiatr Genet, 14(2): 117-20.
Study Design	case-control and family-based
Study Type	Candidate-gene association study
Sample Size	97 nuclear families, 112 patients and 112 controls
Predominant Ethnicity	Caucasian
Population	Canada
Gender	73 male and 24 female probands in the family-based sample; 75 male and 37 female patients, 75 male and 37 female controls in the case-control sample
Age Group	Adults : family-based sample: mean age 32 years, SD=11.93; case-control sample: mean age 38.53 years, SD=10.07 of cases, mean age 38.49 years, SD=10.21 of controls

Detail Info

Summary	They tested for association of the DBH TaqI 2 allele in two independent samples of patients with the persistent variant of ADHD. These consisted of 97 nuclear families, and 112 adult cases with controls carefully matched according to gender, age and ethnicity. Transmission Disequilibrium Test analysis revealed weak over-transmission of the 2 allele. The case-control sample did not support previous findings since the 2 allele was more frequent in our control sample. Taken together, these results do not provide support for a role of the DBH TaqI marker in their persistent ADHD samples.
Total Sample	The family-based sample included 97 nuclear families, which consisted of 57 families with both parents available and 40 families with a single parent. The predominant ethnicity of probands used in the family-based sample was 97.0% mixed European Caucasian. The case-control sample included 112 adult ADHD patients and 112 control subjects. The ethnicity of the case and control subjects: cases, 96.5% Mixed European Caucasian, 1.8% African, 1.3% East Indian, 0.4% Native Canadian; controls, 96.7% Mixed European Caucasian, 2.6% East Indian, 0.4% Native Canadian, 0.3% African.
Sample Collection	Patients were clinician-referred and assessed at the Adult and Adolescent ADHD Research Program of the Centre for Addiction and Mental Health, University of Toronto.
Diagnosis Description	All patients were screened and assessed as previously reported in detail by Muglia et al. (2000, 2002). Diagnosis of ADHD was based on the ADHD DSM-IV criteria, which required complete fulfilment both at the time of interview and during childhood (as recalled by the patient and at least one first-degree relative). For broad assessment of psychiatric conditions, the Structural Clinical Interview for DSM-IV was administered by a trained psychiatrist (U.J.) from the Adult ADHD. All three subcategories of ADHD were considered; however, the vast majority of patients were categorized with the combined subtype of ADHD (no classified cases of hyperactive/impulsive were reported).
Technique	Standard procedures were followed for obtaining blood samples and extracting DNA. The 464 base pair (bp) fragment located on intron 5 of the DBH locus was amplified via polymerase chain reaction techniques using primer sequences from Daly et al. (1999). From the digested 464 bp fragment, TaqI identified a bi-allelic polymorphism. The uncut (TaqI absent) 464 bp fragment was denoted as the 1 allele (A1), while the TaqI digested fragments consisting of 300 bp and 164 bp were assigned as the 2 allele (A2).
Analysis Method	Genotypes for the family-based sample consisting of 97 nuclear families were analysed using the Transmission Disequilibrium Test (TDT) (Spielman et al., 1993). DbH TaqI allele frequencies from their sample of 112 cases and 112 controls were compared using a contingency table to produce a X² value representing the observed distribution of alleles as compared with the expected distribution.
Result Description	Transmission Disequilibrium Test analysis revealed weak over-transmission of the 2 allele (35 transmissions versus 27 non-transmissions; X²=1.03, 1 degree of freedom, P=0.31). The case-control sample did not support previous findings since the 2 allele was more frequent in the control sample (137 versus 116; X²=3.63, 1 degree of freedom, P=0.057).

Other variant reported by this study (count: 1)

Variant Name	Allele Change	Risk Allele	Statistical Values	Author Comments	Result of Statistical Analysis
DBH intron5 C/T TaqI	C/T	2 allele	TDT P-value=0.31, X²=1.03, df=1; TDT P-value=0.12...... TDT P-value=0.31, X²=1.03, df=1; TDT P-value=0.12, X²=2.37, df=1 of males; TDT P-value=0.37, X²=0.82, df=1 of females, for 2 allele in the family-based sample. TDT P-value=0.057, X²=3.63, df=1 for 2 allele in the case-control sample More...	the TDT analysis showed weak over-transmission of the DBH TaqI 2 allele in both samples; the family-based analysis stratified by proband gender revealed that only males were contributing to the biased transmission observed; no gender-specific effects for the case-control sample were observed	Non-significant

Genes reported by this study (count: 1)