BackgroundTo estimate the spectrum of familial risk for psychopathology in first-degree relatives of children with unabridged DSM-IV bipolar-I disorder (BP-I).MethodWe conducted a blinded, controlled family study using structured diagnostic interviews of 157 children with BP-I probands (n=487 first-degree relatives), 162 attention deficit hyperactivity disorder (ADHD) (without BP-I) probands (n=511 first-degree relatives), and 136 healthy control (without ADHD or BP-I) probands (n=411 first-degree relatives).ResultsThe morbid risk (MR) of BP-I disorder in relatives of BP-I probands (MR=0.18) was increased 4-fold [95% confidence interval (CI) 2.3–6.9, p<0.001] over the risk to relatives of control probands (MR=0.05) and 3.5-fold (95% CI 2.1–5.8, p<0.001) over the risk to relatives of ADHD probands (MR=0.06). In addition, relatives of children with BP-I disorder had high rates of psychosis, major depression, multiple anxiety disorders, substance use disorders, ADHD and antisocial disorders compared with relatives of control probands. Only the effect for antisocial disorders lost significance after accounted for by the corresponding diagnosis in the proband. Familial rates of ADHD did not differ between ADHD and BP-I probands.ConclusionsOur results document an increased familial risk for BP-I disorder in relatives of pediatric probands with DSM-IV BP-I. Relatives of probands with BP-I were also at increased risk for other psychiatric disorders frequently associated with pediatric BP-I. These results support the validity of the diagnosis of BP-I in children as defined by DSM-IV. More work is needed to better understand the nature of the association between these disorders in probands and relatives.