Anxiety disorder comobidity in Bipolar I Disorder: relationship to depression severity and treatment outcome.

The present study investigated the greater symptom severity and poorer treatment response found in patients with bipolar illness and anxiety comorbidity, and examined depression as a potential mediator of this relationship. The sample consisted of 92 patients in an acute episode of Bipolar I Disorder with a current or past history of an anxiety disorder. Diagnoses were based on structured clinical interview, and participants were assessed at pre-treatment and then randomly assigned to pharmacotherapy alone or pharmacotherapy plus family intervention. Patients were assessed on a monthly basis by blind assessors over 28 months. Compared to patients without anxiety comorbidity, individuals with bipolar disorder and an anxiety disorder possessed greater current symptom severity, even after controlling for depression severity. Logistic regression analysis identified that being female and having higher current depression but not manic severity predicted comorbid anxiety. Comorbid anxiety was associated with poorer treatment response in the sample regardless of treatment type, particularly in subsequent depressive symptoms. Multiple regression analyses indicated that current depression but not manic severity partially mediated the relationship between comorbid anxiety and treatment outcome. Results from the current study investigating comorbid anxiety disorders are consistent with past research limited to anxiety symptoms. Depression only partially accounted for the link between comorbid anxiety and greater symptom severity and poorer treatment response, and examination of other factors is warranted. Because of the clinical relevance of comorbid anxiety in severe affective disorders, treatments designed to specifically address both concerns are needed.