We examined the antidepressant efficacy and dose-response pattern of the n-3 docosahexaenoic acid (DHA). Thirty-five depressed adult outpatients (46% women; mean age 42+/-14 years) with a 17-item Hamilton-Depression Scale (HAM-D-17) score of >or=18 were randomized into one of three double-blind dosing arms for 12 weeks. Group A (n=14): 1 g/day of oral DHA; Group B (n=11): 2 g/day; and Group C (n=10): 4 g/day.

We measured HAM-D-17 scores, plasma DHA, eicosapentaenoic acid (EPA), and n-6/n-3 ratio. Completer response rates (>or=50% decrease in HAM-D-17 score) were 83% for Group A, 40% for Group B, and 0% for Group C; Groups A and B had significant decreases in HAM-D-17 scores (p<0.05). For completers and intent-to-treat subjects, plasma DHA increased significantly (p<0.05), EPA had little change (p>0.05), and n-6/n-3 decreased significantly (p<0.05).

DHA may be effective for depression at lower doses.