<qa>  What is an atypical antipsychotic drug?This double-blind study will last a total of 12 weeks. Participants will be randomly assigned to receive either olanzapine, an atypical antipsychotic drug, combined with sertraline, an SSRI, or olanzapine alone. Following baseline assessments, study visits will occur weekly until Week 6, and then bi-weekly until Week 12. Participants who do not respond to either treatment may leave the study at any time. Participants who achieve either partial or full response may participate in an additional 20-week study. 