The proposed study is designed to investigate the non-inferiority of treatment of PsyD using monotherapy with quetiapine XR versus combination treatment using quetiapine XR and an SSRI (sertraline or citalopram or escitalopram) during the acute phase of treatment. The primary outcome measures will be the change rates of symptoms of depression (as measured on the Hamilton Rating Scale for Depression [HAM-D-17] and psychosis (as measured on the Brief Psychiatric Rating Scale [BPRS] Positive Symptoms Subscale).