Bipolar II compared with bipolar I disorder: baseline characteristics and treatment response to quetiapine in a pooled analysis of five placebo-controlled clinical trials of acute bipolar depression

BACKGROUND: Bipolar I and II represent the most common and severe subtypes of bipolar disorder. Although bipolar I disorder is relatively well studied, the clinical characteristics and response to treatment of patients with bipolar II disorder are less well understood. METHODS: To compare the severity and burden of illness of patients with bipolar II versus bipolar I disorder, baseline demographic, clinical, and quality of life data were examined in 1900 patients with bipolar I and 973 patients with bipolar II depression, who were enrolled in five similarly designed clinical placebo-controlled trials of quetiapine immediate-release and quetiapine extended-release. Acute (8 weeks) response to treatment was also compared by assessing rating scale scores, including Montgomery–Åsberg depression rating scale, Hamilton rating scale for anxiety, Young mania rating scale, and clinical global impression-severity scores, in the bipolar I and II populations in the same pooled database. RESULTS: Patients with bipolar I and bipolar II depression were similar in demographics, baseline rating scale scores (depression, anxiety, mania, and quality of life), and mood episode histories. Symptom improvements in response to quetiapine were greater versus comparators (lithium, paroxetine, and placebo) at 4 and 8 weeks in both bipolar I and II patients. Patients with the bipolar II subtype initially showed slower responses to all treatments, but, by 8 weeks, attained similar symptom improvement as patients with bipolar I depression. CONCLUSIONS: Pooled analysis of five clinical trials of quetiapine demonstrated that patients with bipolar II depression have a similar burden of illness and quality of life to patients with bipolar I. Bipolar II patients consistently showed a slower response to treatments than bipolar I patients, but, after 8 weeks of treatment with quetiapine, symptom improvements were similar between bipolar I and II disorder subtypes.