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.