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| Christiansen,H.; Chen,W.; Oades,R.D.;
Asherson,P.; Taylor,E.A.; Lasky-Su,J.; Zhou,K.; Banaschewski,T.; Buschgens,C.;
Franke,B.; Gabriels,I.; Manor,I.; Marco,R.; Müller,U.; Mulligan,A.;
Psychogiou,L.; Rommelse,N.; Uebel,H.; Buitelaar,J.; Ebstein,R.; Eisenberg,J.;
Gill,M.; Miranda,A.; Mulas,F.; Gill,M.; Miranda,A.; Rothenberger,A.;
Sergeant,J.A.; Sonuga-Barke,E.J.S.; Steinhausen,H-C.; Thompson,M.; Faraone,S.V. Introduction: Not only is ADHD a common disorder of childhood and adolescence, but so are oppositional defiant disorder (ODD) & conduct disorder (CD). One to two cases of ADHD in three also express ODD or CD as comorbid problems. However, whether comorbid conduct problems (CP) can be considered as a separate disorder or should be viewed as a severe form of ADHD remains controversial. Methods: We studied the recurrence of the pure or comorbid condition in families with two or more children that included one definite case of DSM-IV ADHDct (combined-type) within the context of the International Multicentre ADHD Genetics Study (IMAGE). Diagnosis was made on the basis of the PACS interview (parental accountof childhood symptoms). Symptoms were rated according to the Parent and the Teacher Strengths and Difficulties [SDQ], and the Conners' Questionnaires [CP/TRS]). There were 1009 cases (241 with ADHDonly and 768 with ADHD+CP), and 1591 of their siblings. CP was defined as T>= 4 on the SDQ conduct-subscale, and T>=65, on Conners' oppositional-score. Multinomial logistic regression that took account of the relationship between cases and siblings was used to ascertain recurrence risks of the pure & comorbid conditions in the siblings as predicted by the status of the cases. Results: 1/ Where there were cases with ADHD+CP there was a higher relative risk for siblings to develop ADHD+CP (RRR=4.9; 95%CI: 2.59-9.41: p<0.001) than with ADHDonly. 2/ Rates of ADHDonly in siblings of cases with ADHD+CP were lower - but still significant (RRR=2.9; 95%CI: 1.6-5.3, p<.001). 3/ Ratings on the Conners ADHDct symptom-scales were higher for Children with ADHD+CP than the cases with ADHDonly. Discussion: a) Our finding that ADHD+CP can represent a familial distinct subtype possibly with a distinct genetic etiology is consistent with a high risk for cosegregation. (However, our second result shows that this is not so in all instances.) b) Further, ADHD+CP can be a more severe disorder than ADHDonly with symptoms stable from childhood through adolescence. c) The findings provide partial support for the ICD-10 distinction between hyperkinetic disorder (F90.0) & hyperkinetic conduct disorder (F90.1). Support: NIH.
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