After patients have been on stable treatment with antipsychotic medication for at least 4 weeks, they are randomly assigned to receive antipsychotic medication plus either citalopram or placebo for 3 months. Depressive symptoms and side effects are assessed weekly for the first month, biweekly for the second month, and again at the end of the third month. Cognition, motor and daily functioning, quality of life, and medication adherence are assessed throughout the study.