Pediatric bipolar disorder and ADHD: family history comparison in the LAMS clinical sample

Background: Transgenerational association of bipolar spectrum disorder (BPSD) and attention deficit/hyperactivity disorder (ADHD) has been reported, but inconclusively.

Method: Children ages 6-12 were systematically recruited at first outpatient visit at 9 clinics at four universities and reliably diagnosed; 621 had elevated symptoms of mania (>12 on the Parent General Behavior Inventory 10-Item Mania Scale); 86 had scores below 12. We analyzed baseline data to test a familial association hypothesis: compared to children with neither BPSD nor ADHD, those with either BPSD or ADHD would have parents with higher rates of both bipolar and ADHD symptoms, and parents of comorbid children would have even higher rates of both.

Results: Of 707 children, 421 had ADHD without BPSD, 45 BPSD without ADHD, 117 comorbid ADHD+BPSD, and 124 neither. The rate of parental manic symptoms was similar for the comorbid and BPSD-alone groups, significantly greater than for ADHD alone and "neither" groups, which had similar rates. ADHD symptoms in parents of children with BPSD alone were significantly less frequent than in parents of children with ADHD (alone or comorbid), and no greater than for children with neither diagnosis. Family history of manic symptoms, but not ADHD symptoms, was associated with parent-rated child manic-symptom severity over and above child diagnosis.

Limitations: The sample was not epidemiologic, parent symptoms were based on family history questions, and alpha was 0.05 despite multiple tests.

Conclusions: These results do not support familial linkage of BPSD and ADHD; they are compatible with heritability of each disorder separately with coincidental overlap.