Pediatric bipolar spectrum disorder and ADHD: comparison and comorbidity in the LAMS clinical sample.

OBJECTIVE: To compare attention-deficit hyperactivity disorder (ADHD), bipolar spectrum disorders (BPSDs), and comorbidity in the Longitudinal Assessment of Manic Symptoms (LAMS) study.
METHODS: Children ages 6-12 were recruited at first visit to clinics associated with four universities. A BPSD diagnosis required that the patient exhibit episodes. Four hypotheses were tested: (i) children with BPSD + ADHD would have a younger age of mood symptom onset than those with BPSD but no ADHD; (ii) children with BPSD + ADHD would have more severe ADHD and BPSD symptoms than those with only one disorder; (iii) global functioning would be more impaired in children with ADHD + BPSD than in children with either diagnosis alone; and (iv) the ADHD + BPSD group would have more additional diagnoses.
RESULTS: Of 707 children, 421 had ADHD alone, 45 had BPSD alone, 117 had both ADHD and BPSD, and 124 had neither. Comorbidity (16.5%) was slightly less than expected by chance (17.5%). Age of mood symptom onset was not different between the BPSD + ADHD group and the BPSD-alone group. Symptom severity increased and global functioning decreased with comorbidity. Comorbidity with other disorders was highest for the ADHD + BPSD group, but higher for the ADHD-alone than the BPSD-alone group. Children with BPSD were four times as likely to be hospitalized (22%) as children with ADHD alone.
CONCLUSIONS: The high rate of BPSD in ADHD reported by some authors may be better explained as a high rate of both disorders in child outpatient settings rather than ADHD being a risk factor for BPSD. Co-occurrence of the two disorders is associated with poorer global functioning, greater symptom severity, and more additional comorbidity than for either single disorder.