BACKGROUND: In depressed patients, low blood levels of eicosapentaenoic acid are seen. We tested the antidepressive effect of ethyl-eicosapentaenoate in these patients.

METHODS: We included 70 patients with persistant depression despite ongoing treatment with an adequate dose of a standard antidepressant. Patients were randomized on a double-blind basis to placebo or ethyl-eicosapentaenoate at dosages of 1, 2, or 4 g/d for 12 weeks in addition to unchanged background medication. Patients underwent assessment using the 17-item Hamilton Depression Rating Scale, the Montgomery-Asberg Depression Rating Scale, and the Beck Depression Inventory.

RESULTS: Forty-six (88%) of 52 patients receiving ethyl-eicosapentaenoate and 14 (78%) of 18 patients receiving placebo completed the 12-week study with no serious adverse events. The 1-g/d group showed a significantly better outcome than the placebo group on all 3 rating scales. In the intention-to-treat group, 5 (29%) of 17 patients receiving placebo and 9 (53%) of 17 patients receiving 1 g/d of ethyl-eicosapentaenoate achieved a 50% reduction on the Hamilton Depression Rating Scale score. In the per-protocol group, the corresponding figures were 3 (25%) of 12 patients for placebo and 9 (69%) of 13 patients for the 1-g/d group. The 2-g/d group showed little evidence of efficacy, whereas the 4-g/d group showed nonsignificant trends toward improvement. All of the individual items on all 3 rating scales improved with the 1-g/d dosage of ethyl-eicosapentaenoate vs placebo, with strong beneficial effects on items rating depression, anxiety, sleep, lassitude, libido, and suicidality.

CONCLUSION: Treatment with ethyl-eicosapentaenoate at a dosage of 1 g/d was effective in treating depression in patients who remained depressed despite adequate standard therapy.