Effects of n-3 fatty acids on depressive symptoms and dispositional optimism after myocardial infarction.

Randomized, double-blind, placebo-controlled trial in adults after myocardial infarction, a coronary heart disease population. Active intervention arms included EPA-DHA plus ALA, EPA-DHA alone, and ALA alone; reported randomized Ns for the active arms were 1,021, 1,015, and 1,034, respectively, in a 1:1:1:1 allocation design.

Participants received oral margarines for 40 months containing either 400 mg/day EPA-DHA, 2 g/day ALA, both EPA-DHA plus ALA, or placebo margarine with oleic acid substituted for the active oils. The regimen tested low-dose n-3 fatty acids delivered daily in a blinded, placebo-controlled format.

Low-dose EPA-DHA, ALA, or their combination did not improve depressive symptoms or dispositional optimism after myocardial infarction. At 40 months, depressive symptoms on the GDS-15 were not significantly different from placebo: EPA-DHA plus ALA standardized mean difference -0.025 (P = 0.57), EPA-DHA -0.048 (P = 0.28), and ALA -0.047 (P = 0.29); two-way analyses were also nonsignificant. Severe depressive symptoms remained uncommon and did not differ meaningfully from placebo: adjusted OR 1.00 for EPA-DHA plus ALA, 1.29 for EPA-DHA, and 1.40 for ALA. Dispositional optimism results were likewise largely null, with no consistent significant between-group differences, and adverse events such as gastrointestinal or other health problems did not differ across groups.

Depressive symptoms and pessimism/optimism were low at baseline, leaving limited room for improvement. The intervention tested relatively low-dose n-3 fatty acids, so null findings may not generalize to higher-dose regimens or patients with greater symptom burden. Outcomes were largely self-reported and the few borderline p-values were not consistent across measures.