“…Among the internalizing disorders, the prevalence of co -occurrence is somewhat lower with 10% to 20% of children with ADHD exhibiting mood disorder (Acosta et al, 2004;Eiraldi, Power, & Nezu, 1997;Sanders et al, 2005;. In addition, the association of ADHD with both depressive disorders and anxiety disorders has been replicated by new epidemiological studies (Angold, Costello, & Erkanli, 1999;Costello, Egger, & Angold, 2005). It is now clear that assessment of the underlying structure of these disorders, to discriminate natural symptom aggregation across ADHD domains and provide insight into the cause of comorbidity, is necessary to better understand the psychopathology of these entities.…”