Quetiapine in Melancholic Depression

In summary, the investigators propose to integrate fMRI assessments within a clinical trial of quetiapine XR in patients with melancholic depression in order to test the predictions that: 1. quetiapine XR treatment will be effective and safe for patients with major depression with melancholic features 2. successful treatment with quetiapine XR will be associated with normalization of limbic areas associated with increased salivary cortisol response to a stressful task as well as normalization on the emotional faces task differences in the melancholic group compared with healthy volunteers. 3. successful treatment with quetiapine XR will be associated with normalization of the salivary cortisol response to the stressful math task (i.e. there will be a diminished post-treatment mean AUC for cortisol secretion after the stress task compared to the pre-treatment AUC values in the patient group)