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The impact of study design and diagnostic approach in a large multi-centre ADHD study: part 2: dimensional measures of psychopathology and intelligence

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Abstract
Background: The International Multi-centre ADHD Genetics (IMAGE) project with 11 participating centres from 7 European countries and Israel has collected a large behavioural and genetic database for present and future research. Behavioural data were collected from 1068 probands with ADHD and 1446 unselected siblings. The aim was to describe and analyse questionnaire data and IQ measures from all probands and siblings. In particular, to investigate the influence of age, gender, family status (proband vs. sibling), informant, and centres on sample homogeneity in psychopathological measures. Methods: Conners' Questionnaires, Strengths and Difficulties Questionnaires, and Wechsler Intelligence Scores were used to describe the phenotype of the sample. Data were analysed by use of robust statistical multi-way procedures. Results: Besides main effects of age, gender, informant, and centre, there were considerable interaction effects on questionnaire data. The larger differences between probands and siblings at home than at school may reflect contrast effects in the parents. Furthermore, there were marked gender by status effects on the ADHD symptom ratings with girls scoring one standard deviation higher than boys in the proband sample but lower than boys in the siblings sample. The multi-centre design is another important source of heterogeneity, particularly in the interaction with the family status. To a large extent the centres differed from each other with regard to differences between proband and sibling scores. Conclusions: When ADHD probands are diagnosed by use of fixed symptom counts, the severity of the disorder in the proband sample may markedly differ between boys and girls and across age, particularly in samples with a large age range. A multi-centre design carries the risk of considerable phenotypic differences between centres and, consequently, of additional heterogeneity of the sample even if standardized diagnostic procedures are used. These possible sources of variance should be counteracted in genetic analyses either by using age and gender adjusted diagnostic procedures and regional normative data or by adjusting for design artefacts by use of covariate statistics, by eliminating outliers, or by other methods suitable for reducing heterogeneity.
Keywords
CHILD PSYCHIATRIC-PATIENTS, CONDUCT DISORDER, DEFICIT HYPERACTIVITY DISORDER, ATTENTION-DEFICIT/HYPERACTIVITY DISORDER, CRITERION VALIDITY, METAANALYSIS, SIBLINGS, PARENT, TWIN, RELIABILITY, ADHD multi-centre study, sibling design, centre effects

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Chicago
Muller, Ueli C, Philip Asherson, Tobias Banaschewski, Jan K Buitelaar, Richard P Ebstein, Jaques Eisenberg, Michael Gill, et al. 2011. β€œThe Impact of Study Design and Diagnostic Approach in a Large Multi-centre ADHD Study: Part 2: Dimensional Measures of Psychopathology and Intelligence.” Bmc Psychiatry 11.
APA
Muller, U. C., Asherson, P., Banaschewski, T., Buitelaar, J. K., Ebstein, R. P., Eisenberg, J., Gill, M., et al. (2011). The impact of study design and diagnostic approach in a large multi-centre ADHD study: part 2: dimensional measures of psychopathology and intelligence. BMC PSYCHIATRY, 11.
Vancouver
1.
Muller UC, Asherson P, Banaschewski T, Buitelaar JK, Ebstein RP, Eisenberg J, et al. The impact of study design and diagnostic approach in a large multi-centre ADHD study: part 2: dimensional measures of psychopathology and intelligence. BMC PSYCHIATRY. 2011;11.
MLA
Muller, Ueli C et al. β€œThe Impact of Study Design and Diagnostic Approach in a Large Multi-centre ADHD Study: Part 2: Dimensional Measures of Psychopathology and Intelligence.” BMC PSYCHIATRY 11 (2011): n. pag. Print.
@article{1968436,
  abstract     = {Background: The International Multi-centre ADHD Genetics (IMAGE) project with 11 participating centres from 7 European countries and Israel has collected a large behavioural and genetic database for present and future research. Behavioural data were collected from 1068 probands with ADHD and 1446 unselected siblings. The aim was to describe and analyse questionnaire data and IQ measures from all probands and siblings. In particular, to investigate the influence of age, gender, family status (proband vs. sibling), informant, and centres on sample homogeneity in psychopathological measures. Methods: Conners' Questionnaires, Strengths and Difficulties Questionnaires, and Wechsler Intelligence Scores were used to describe the phenotype of the sample. Data were analysed by use of robust statistical multi-way procedures. Results: Besides main effects of age, gender, informant, and centre, there were considerable interaction effects on questionnaire data. The larger differences between probands and siblings at home than at school may reflect contrast effects in the parents. Furthermore, there were marked gender by status effects on the ADHD symptom ratings with girls scoring one standard deviation higher than boys in the proband sample but lower than boys in the siblings sample. The multi-centre design is another important source of heterogeneity, particularly in the interaction with the family status. To a large extent the centres differed from each other with regard to differences between proband and sibling scores. Conclusions: When ADHD probands are diagnosed by use of fixed symptom counts, the severity of the disorder in the proband sample may markedly differ between boys and girls and across age, particularly in samples with a large age range. A multi-centre design carries the risk of considerable phenotypic differences between centres and, consequently, of additional heterogeneity of the sample even if standardized diagnostic procedures are used. These possible sources of variance should be counteracted in genetic analyses either by using age and gender adjusted diagnostic procedures and regional normative data or by adjusting for design artefacts by use of covariate statistics, by eliminating outliers, or by other methods suitable for reducing heterogeneity.},
  articleno    = {55},
  author       = {Muller, Ueli C and Asherson, Philip and Banaschewski, Tobias and Buitelaar, Jan K and Ebstein, Richard P and Eisenberg, Jaques and Gill, Michael and Manor, Iris and Miranda, Ana and Oades, Robert D and Roeyers, Herbert and Rothenberger, Aribert and Sergeant, Joseph A and Barke, Edmund and Thompson, Margaret and Faraone, Stephen V and Steinhausen, Hans-Christoph},
  issn         = {1471-244X},
  journal      = {BMC PSYCHIATRY},
  keywords     = {CHILD PSYCHIATRIC-PATIENTS,CONDUCT DISORDER,DEFICIT HYPERACTIVITY DISORDER,ATTENTION-DEFICIT/HYPERACTIVITY DISORDER,CRITERION VALIDITY,METAANALYSIS,SIBLINGS,PARENT,TWIN,RELIABILITY,ADHD multi-centre study,sibling design,centre effects},
  language     = {eng},
  pages        = {17},
  title        = {The impact of study design and diagnostic approach in a large multi-centre ADHD study: part 2: dimensional measures of psychopathology and intelligence},
  url          = {http://dx.doi.org/10.1186/1471-244X-11-55},
  volume       = {11},
  year         = {2011},
}

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