The present study aimed at: (1) exploring rate and clinical features of superimposed bipolar disorder (BD) in Italian children with attention deficit hyperactivity disorder (ADHD), compared with a community sample, matched for age and gender; (2) exploring predictors of BD in ADHD children, by comparing ADHD children with or without superimposed BD. We studied 173 consecutive drug-naïve outpatients with ADHD (156 males and 17 females, mean age of 9.2 ± 2.3years, age range 6-17.5 years), diagnosed with a clinical interview (Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (K-SADS-PL)); the control group consisted of a community-based sample of 100 healthy children. The rate of children with a diagnosis of BD was higher in the ADHD group (29/173, 16.7%) compared with controls (1/100, 1%), (P<0.001). Among the 29 children with ADHD+BD, 16 (55.2%) had a Bipolar Disorder-Not Otherwise Specified (BD-NOS), and 11 (37.9%) showed ultrarapid cycling. Compared with children with ADHD without BD, they showed a higher rate of combined sub-type (21/29, 72.4%), a higher score at ADHD-Rating Scale (total score and hyperactivity subscale), higher rates of major depression, oppositional defiant disorder and conduct disorder. In summary, children with ADHD present a higher risk for developing a superimposed BD. The identification of clinical features with an increased risk of BD can improve diagnosis, prognosis and treatments.
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