The Effects of Quetiapine XR on Cognition, Mood and Anxiety Symptoms in SSRI-Resistant Unipolar Depression

Recently published work has examined the effects of "atypical antipsychotics" in SSRI-treatment resistant patients. In these studies, patients with unipolar depression who were treated with SSRI's, but not responsive to treatment after 4 or more weeks, were supplemented with an atypical. The atypical antipsychotics were found to diminish depression symptoms, as well as benefit sleep quality. We propose a similar study with Quetiapine XR, focusing on thinking processes, mood and anxiety. Patients with depression who are SSRI treatment resistant will be treated with Quetiapine. Cognition will be evaluated in the UBC Mood Disorders Clinic two times: first before Quetiapine addition, then after 8 weeks. Depression symptoms and other measurements will be done at the 9 time points: before Quetiapine, and each week after treatment has begun. The primary purpose of this study is to evaluate the superiority of Quetiapine XR compared to placebo as augmentation therapy in treatment of anxiety and depressive symptoms in SSRI-nonresponsive unipolar patients. Secondarily, we would like to evaluate the safety and tolerability of quetiapine as augmentation therapy in SSRI-nonresponsive unipolar patients.