 Motivational Interviewing MI is a time-limited psychotherapy that has successfully improved treatment retention among patients with dually diagnosed substance abuse and psychiatric disorders. During Phase I of this study, MI is adapted for use as an adjunctive therapy with antidepressant treatment and culturally adapted to Hispanic participants. In Phase II, participants receive sertraline for 12 weeks and participate in four sessions of MI therapy as a supplementary intervention designed to encourage treatment retention. Participants who are intolerant to sertraline or have an inadequate response by Week 6 are switched to venlafaxine ER while continuing to receive MI and to complete study assessments. A follow-up interview is conducted 6 months after the termination of treatment. 