The aim of the study is to examine the efficacy of omega-3 fatty acid as an adjunct to ongoing pharmacological treatments in patients with residual symptoms of depression and anxiety.

This randomized, double-blind, placebo-controlled, cross-over trial was conducted at a single private practice site. Participants were drawn from patients attending the practice.

Patients meeting criteria had a 4-week run-in period where they continued to receive their prescribed medications and omega-3 supplements. Depression and anxiety ratings were assessed at recruitment and completion of the run-in phase. Patients were randomized to receive an omega-3 supplement (Neurospark) or placebo once daily for 8 weeks then crossed over to the alternative treatment. At the end of the double-blind, cross-over phase, patients received the supplement and were assessed after a 4-week run-out phase.

Depression and anxiety symptoms were assessed using the Hamilton scales. Efficacy of treatment was assessed using a linear mixed model analysis with time, order of treatment, diagnosis, and their interaction as factors. Depression and anxiety scales were analyzed as independent measures.

The study enrolled 47 patients (mean [SD] age, 46.1 [11.2] years; [59.6%] male). Depression scores did not significantly change across assessments (P > 0.1); there was no effect of order of treatment (P > 0.1) or an interaction between time, order of treatment, and psychiatric diagnosis (P > 0.1). Anxiety scores were similarly unchanged across treatment visits and order of treatment, and there was no interaction between time, order of treatment, and psychiatric diagnosis.

Omega-3 fatty acid supplementation did not significantly alter residual symptoms in this group of patients.