Quetiapine in Co-Morbid Depressive and Anxiety Disorders

The primary objective is to examine the beneficial effect of quetiapine augmentation of first-line antidepressants in refractory depression with co-morbid anxiety, compared to placebo. It is hypothesized that significant improvement on depression and anxiety symptoms will be seen as evidenced by reduction in Hamilton Depression Rating Scale (HAMD-17) and Hamilton Anxiety Scale (HAMA) scores after the 12 week treatment period for those who received Quetiapine XR augmentation compared to those who received placebo.2.2 Secondary objectives: 1) To establish the tolerability and safety of Quetiapine XR versus Placebo in patients with co-morbid depressive and anxiety disorders;2) To assess and compare the efficacy of Quetiapine XR versus Placebo improving quality of life in patients with co-morbid depressive and anxiety disorders.; 3) To assess and compare the efficacy of Quetiapine XR versus Placebo on clinical measures symptoms associated to co-morbid depressive and anxiety disorders.