Brief report Dysthymic disorder contributes to oppositional defiant behaviour in children with Attention Deficit Hyperactivity Disorder, combined type (ADHD-CT) Alasdair Vance T , Michelle Sanders, Yolanda Arduca Academic Child Psychiatry Unit, Department of Paediatrics, University of Melbourne, Royal Children’s Hospital, Murdoch Children’s Research Institute, Parkville, VIC 3052, Australia Received 26 November 2004; received in revised form 8 March 2005; accepted 9 March 2005 Abstract Background: The specific relationships between oppositional defiant disorder (ODD), ADHD-CT, dysthymic disorder (DD) and anxiety disorders symptoms have not been studied in children with ADHD-CT. The relationship to DD is important because DD is common, has an earlier age of onset, is associated with significant morbidity and with increased rates of treatment non- responsiveness when comorbid with major depressive disorder and/or ADHD-CT. Methods: 200 clinically referred children with ADHD-CT, without comorbid major depressive disorder, were identified. dODDT, dADHD-CTT , dDDT and danxiety disordersT symptoms were defined by composite measures of (1) semi-structured clinical interview and (2) parent and/or child standardized questionnaires. Standard multiple regression was used to examine how well dADHD-CTT , dDDT and danxiety disordersT symptoms predict dODDT symptoms. Results: Only dADHD-CTT (15% of the variance) and dDDT (8% of the variance) symptoms made independent significant contributions to the prediction of dODDT symptoms. Limitations: The study’s sample size did not allow dODDT and dconduct disorderT symptoms to be analysed separately. Conclusions: The association of DD with ODD may reflect a unique contribution of DD to ODD in children, whether ADHD- CT is present or not, or only when ADHD-CT is present. D 2005 Elsevier B.V. All rights reserved. Keywords: ADHD; Combined type; Dysthymic disorder; Oppositional defiant disorder 1. Introduction The greater than chance association of oppositional defiant disorder (ODD) with Attention Deficit Hyper- activity Disorder, combined type (ADHD-CT), depressive disorders and anxiety disorders is a 0165-0327/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2005.03.007 T Corresponding author. Tel.: +61 3 9345 4666; fax: +61 3 9345 6002. E-mail address: avance@unimelb.edu.au (A. Vance). Journal of Affective Disorders 86 (2005) 329 – 333 www.elsevier.com/locate/jad