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	Johnson KA, 200818361436
Citation	Johnson K. A., Kelly S. P., Robertson I. H., Barry E., Mulligan A., Daly M., Lambert D., McDonnell C., Connor T. J., Hawi Z., Gill M. and Bellgrove M. A. (2008) "Absence of the 7-repeat variant of the DRD4 VNTR is associated with drifting sustained attention in children with ADHD but not in controls." Am J Med Genet B Neuropsychiatr Genet, 147B(6): 927-37.
Study Design	case-control
Study Type	Candidate-gene association study
Sample Size	68 ADHD patients and 60 controls
Predominant Ethnicity	Caucasian
Population	Ireland
Age Group	Children/Adolescents : 11.4 (SD=2.3) years for cases, 11.8 (SD=3.2) years for controls

Detail Info

Summary	They investigated the performance of 128 children with and without ADHD on the Fixed and Random versions of the Sustained Attention to Response Task (SART). They employed time-series analyses of reaction-time data to allow a fine-grained analysis of reaction time variability, a candidate endophenotype for ADHD. Children were grouped into either the 7r-present group (possessing at least one copy of the 7r allele) or the 7r-absent group. The ADHD group made significantly more commission errors and was significantly more variable in RT in terms of fast moment-to-moment variability than the control group, but no effect of genotype was found on these measures. Children with ADHD without the 7r allele made significantly more omission errors, were significantly more variable in the slow frequency domain and showed less sensitivity to the signal (d') than those children with ADHD the 7r and control children with or without the 7r. These results highlight the utility of time-series analyses of reaction time data for delineating the neuropsychological deficits associated with ADHD and the DRD4 VNTR. Absence of the 7-repeat allele in children with ADHD is associated with a neurocognitive profile of drifting sustained attention that gives rise to variable and inconsistent performance.
Total Sample	Sixty-eight children with ADHD and 60 control children participated in the study. All children were of Irish descent. There was no significant difference in age between the two groups. The participants were recruited as part of ongoing genetic studies. The control children were recruited from Dublin schools.
Sample Collection	Irish descent
Diagnosis Description	Diagnosis for the ADHD participants was confirmed by psychiatrists using the parent form of the Child and Adolescent Psychiatric Assessment (CAPA).
Technique	The procedures followed for genotyping the ADHD and control samples have been previously published [Hawi et al., 2000].
Analysis Method	All dependent variables were calculated per participant. All measures were analyzed in a Diagnosis (ADHD vs. control) by SART (Fixed vs. Random) by Genotype (7-present vs. 7-absent) three-way mixed factorial ANOVA design. The alpha level was set at 0.05.
Result Description	There was a significant association between possession of the 7-repeat allele and diagnosis, with more of the children with ADHD in possession of the 7-repeat allele (28 out of 68) than the control group (15 out of 60).

Other variant reported by this study (count: 1)

Genes reported by this study (count: 1)