title: Familiality of Co-existing ADHD and Tic Disorders: Evidence from a Large Sibling Study.
abstract: BACKGROUND
  The association of attention-deficit/hyperactivity disorder (ADHD) and tic disorder (TD) is frequent and clinically important. Very few and inconclusive attempts have been made to clarify if and how the combination of ADHD+TD runs in families.
  
  
  OBJECTIVE
  To determine the first time in a large-scale ADHD sample whether ADHD+TD increases the risk of ADHD+TD in siblings and, also the first time, if this is independent of their psychopathological vulnerability in general.
  
  
  METHODS
  The study is based on the International Multicenter ADHD Genetics (IMAGE) study. The present sub-sample of 2815 individuals included ADHD-index patients with co-existing TD (ADHD+TD, n = 262) and without TD (ADHD-TD, n = 947) as well as their 1606 full siblings (n = 358 of the ADHD+TD index patients and n = 1248 of the ADHD-TD index patients). We assessed psychopathological symptoms in index patients and siblings by using the Strength and Difficulties Questionnaire (SDQ) and the parent and teacher Conners' long version Rating Scales (CRS). For disorder classification the Parental Account of Childhood Symptoms (PACS-Interview) was applied in n = 271 children. Odds ratio with the GENMOD procedure (PROCGENMOD) was used to test if the risk for ADHD, TD, and ADHD+TD in siblings was associated with the related index patients' diagnoses. In order to get an estimate for specificity we compared the four groups for general psychopathological symptoms.
  
  
  RESULTS
  Co-existing ADHD+TD in index patients increased the risk of both comorbid ADHD+TD and TD in the siblings of these index patients. These effects did not extend to general psychopathology.
  
  
  CONCLUSIONS
  Co-existence of ADHD+TD may segregate in families. The same holds true for TD (without ADHD). Hence, the segregation of TD (included in both groups) seems to be the determining factor, independent of further behavioral problems. This close relationship between ADHD and TD supports the clinical approach to carefully assess ADHD in any case of TD.
authors.affiliation: Department of Child and Adolescent Psychiatry and Psychotherapy, Dresden University of Technology Dresden, Germany.
authors.forename: Veit
authors.initials: V
authors.lastname: Roessner
authors.affiliation: Department of Child and Adolescent Psychiatry and Psychotherapy, Central Institute of Mental Health Mannheim, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Banaschewski
authors.affiliation: Department of Child and Adolescent Psychiatry and Psychotherapy, University Medical Center Göttingen Goettingen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Becker
authors.affiliation: Department of Child and Adolescent Psychiatry and Psychotherapy, Dresden University of Technology Dresden, Germany.
authors.forename: Judith
authors.initials: J
authors.lastname: Buse
authors.affiliation: Department of Child and Adolescent Psychiatry and Psychotherapy, Dresden University of Technology Dresden, Germany.
authors.forename: Sina
authors.initials: S
authors.lastname: Wanderer
authors.affiliation: Department of Cognitive Neuroscience, Radboud University Nijmegen Medical Center Nijmegen, Netherlands.
authors.forename: Jan K
authors.initials: JK
authors.lastname: Buitelaar
authors.affiliation: Department of Clinical Neuropsychology, Vrije Universiteit Amsterdam Amsterdam, Netherlands.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Sergeant
authors.affiliation: Developmental Brain Behaviour Laboratory, School of Psychology, University of Southampton Southampton, UK.
authors.forename: Edmund J
authors.initials: EJ
authors.lastname: Sonuga-Barke
authors.affiliation: Department of Psychiatry, Trinity Centre for Health Sciences Dublin, Ireland.
authors.forename: Michael
authors.initials: M
authors.lastname: Gill
authors.affiliation: ADHD Unit, Geha Mental Health Centre Petach-Tiqva, Israel.
authors.forename: Iris
authors.initials: I
authors.lastname: Manor
authors.affiliation: Department of Developmental and Educational Psychology, University of Valencia Valencia, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Miranda
authors.affiliation: Neuropediatrics Unit, La Fe University Hospital Valencia, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Mulas
authors.affiliation: Department of Child and Adolescent Psychiatry, University of Duisburg-Essen Essen, Germany.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Oades
authors.affiliation: Department of Clinical and Experimental Psychology, Ghent University Ghent, Belgium.
authors.forename: Herbert
authors.initials: H
authors.lastname: Roeyers
authors.affiliation: Department of Child and Adolescent Psychiatry, University of Zurich Zurich, Switzerland.
authors.forename: Hans-Christoph
authors.initials: HC
authors.lastname: Steinhausen
authors.affiliation: Departments of Psychiatry, Neuroscience and Physiology, State University of New York Upstate Medical University New York, NY, USA.
authors.forename: Steven V
authors.initials: SV
authors.lastname: Faraone
authors.affiliation: Institute of Psychiatry, King's College London London, UK.
authors.forename: Philip
authors.initials: P
authors.lastname: Asherson
authors.affiliation: Department of Child and Adolescent Psychiatry and Psychotherapy, University Medical Center Göttingen Goettingen, Germany.
authors.forename: Aribert
authors.initials: A
authors.lastname: Rothenberger
keywords: ADHD; CRS-L; IMAGE; SDQ; comorbidity; familiality; tic disorders