OBJECTIVE:The objective of this study was to explore the efficacy of combination therapy with citalopram plus omega-3 fatty acids versus citalopram plus placebo (olive oil) in the initial treatment of individuals with major depressive disorder (MDD). We hypothesized that combination therapy would lead not only to greater efficacy but also to a more rapid onset of therapeutic response. METHODS:Forty-two subjects participated in this 9-week randomized, masked, placebo-controlled study of combination therapy (two 1 g capsules containing a blend of 900 mg of eicosapentaenoic acid, 200 mg of and docosahexaenoic acid, and 100 mg of other omega-3 fatty acids twice daily plus citalopram) versus monotherapy (two 1 g capsules of olive oil per day plus citalopram) treatment of MDD. RESULTS:The combination therapy demonstrated significantly greater improvement in Hamilton Depression Rating scale scores over time (F = 7.32; df 1,177; P = 0.008) beginning at week 4 (t = -2.48; df 177; P = 0.014). CONCLUSIONS:Combination therapy was more effective than monotherapy in decreasing signs and symptoms of MDD during the 8 weeks of active treatment; however, combination therapy did not seem to enhance the speed of the initial antidepressant response. These findings suggest that there may be an advantage to combining omega-3 fatty acids with a selective serotonin uptake inhibitor in the initial treatment of individuals with MDD. A larger definitive study is warranted.