Comorbid anxiety in phenotypes of pediatric bipolar disorder.

OBJECTIVE: There has been limited research on anxiety in pediatric bipolar disorder (BPD). Adult BPD studies suggest comorbid anxiety disorders are common and impact treatment outcome. We explored the association of comorbid anxiety with two phenotypes of pediatric BPD.
METHODS: We studied two groups of children. The first group (BPD; N = 31) represents the "narrow phenotype" of pediatric BPD, meeting stringent DSM-IV criteria for mania, including duration and elevated/expansive mood. The second group (ED; N = 32) exhibited chronic, non-episodic irritability without elation or grandiosity ("broad phenotype").
RESULTS: Both samples demonstrate high prevalence of anxiety (BPD 77.4%; ED 46.9%). In the BPD sample, anxiety predates BPD onset, and those with comorbid anxiety have earlier age of onset of BPD than those without. Children with BPD plus anxiety have more hospitalizations than those without anxiety. ED subjects with and without comorbid anxiety did not differ with respect to onset of ED symptoms or number of hospitalizations.
CONCLUSIONS: Narrow and broad phenotype BPD children have high rates of comorbid anxiety, although only in the narrow phenotype group is comorbid anxiety associated with greater functional impairment BPD plus comorbid anxiety may represent a particularly severe phenotype of pediatric BPD.