Dysthymic disorder contributes to oppositional defiant behaviour in children with Attention Deficit Hyperactivity Disorder, combined type (ADHD-CT)

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 nonresponsiveness 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. 'ODD', 'ADHD-CT', 'DD' and 'anxiety disorders' 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 'ADHD-CT', 'DD' and 'anxiety disorders' symptoms predict 'ODD' symptoms. Results: Only 'ADHD-CT' (15% of the variance) and 'DD' (8% of the variance) symptoms made independent significant contributions to the prediction of 'ODD' symptoms. Limitations: The study's sample size did not allow 'ODD' and 'conduct disorder' symptoms to be analysed separately. Conclusions: The association of DD with ODD may reflect a unique contribution of DD to ODD in children, whether ADHDCT is present or not, or only when ADHD-CT is present. (c) 2005 Elsevier B.V. All rights reserved.