Patients, ages 18 and over, with a diagnosis of major depression (without psychotic features), will be titrated onto an isoflavone mixture, Novasoy® (Registered Trademark), to a specific target dose (genistin &eq; 270mg/day in divided doses). At the end of week 5 nonresponders (less or equal to 50% improvement) will have one further titration to a higher dose (genistin&eq;360 mg/day in divided doses). Primary efficacy will be determined by demonstrating a greater response rate using a well-validated rating scale. Subjects will be randomized 1:1 with stratification for sex. Improvement in depressive symptoms is hypothesized to be significantly greater in the active soy isoflavone group.