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	Tahir E, 2000 (a)10898901
Citation	Tahir E., Curran S., Yazgan Y., Ozbay F., Cirakoglu B. and Asherson P. J. (2000) "No association between low- and high-activity catecholamine-methyl-transferase (COMT) and attention deficit hyperactivity disorder (ADHD) in a sample of Turkish children." Am J Med Genet, 96(3): 285-8.
Study Design	family-based
Study Type	Candidate-gene association study
Sample Size	72 trios
Predominant Ethnicity	Turkish
Population	Turkey
Age Group	Children/Adolescents

Detail Info

Summary	Biochemical and genetic studies of attention deficit hyperactivity disorder (ADHD) suggest that regulation of catecholamine neurotransmission is a key factor in the aetiology of the disorder. In particular, it is postulated that an underactive dopamine system is associated with the disorder. In this study they tested this hypothesis by screening a clinical sample of Turkish children with the combined subtype of ADHD with a functional variant of catecholamine-methyl-transferase (COMT) that codes for high- and low-activity variants of the enzyme. Using within-family tests of association and linkage in a sample of 72 children, no evidence was found for a genetic association or linkage. They concluded that altered regulation of catecholamines due to this polymorphism does not have a significant main effect on the risk for ADHD in this population. However, it remains feasible that more minor effects or interacting effects with other genes or environment exist.
Total Sample	The Nla III polymorphism was genotyped in 72 trios consisting of Turkish children with Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) diagnoses of the combined subtype of ADHD and their parents. Comorbid diagnoses were made for Tourette's syndrome or tics in 34%, conduct disorder/oppositional defiant disorder in 25%, and depression in 8% of the children.
Sample Collection	The probands were identified from a child behavioural/neuropsychiatric clinic at Marmara University Medical School, Istanbul, and given a research assessment if they were thought to have a diagnosis of ADHD.
Diagnosis Description	A definite DSM-IV diagnosis of ADHD and comorbid conditions were confirmed by two child psychiatrists following a semistructured interview based on K-SADS with the parents and the child. Pervasiveness of hyperactivity symptoms were confirmed from teacher reports. Cases were excluded if major neurological disorders were present such as head injury, epilepsy, or fragile X syndrome and if IQ scores were less than 80. Several rating scales were used to provide dimensional measures of symptom domains and to provide comparability with data from other groups; these included a DSM-IV item checklist, Connors parent and teacher rating scales, and the Child Behavioral Checklist (CBCL) with the associated teacher (TRF) version. Finally, response to methylphenidate was defined if there was an improvement of at least 50% on a clinical global impression scale administered before and after treatment with methylphenidate over 6 weeks.
Technique	High molecular weight DNA was extracted from venous blood using routine procedures. Each individual was typed for high and low COMT activity by amplification of a 169-bp fragment using PCR.
Analysis Method	Analyses were carried out using both transmission disequilibrium test (TDT) and haplotype-based haplotype relative risk (HHRR) procedures.
Result Description	None of these analyses provide any evidence of an association between this functional COMT polymorphism and ADHD. None of these tests provided any evidence for a role of the COMT polymorphism in these phenotypic variables.

SNPs reported by this study (count: 1)

Genes reported by this study (count: 1)