Do Omega-3 Fatty Acids Have an Antidepressant Effect in Patients With Signs of Peripheral Inflammation?

In this study, the investigators will stratify depressed subjects a priori based on CRP levels to test the hypothesis that eicosapentaenoic (EPA) would be more efficacious to treat depression in subjects with high CRP levels compared to subjects with low CRP levels. Depressed subjects, with ongoing stabilized antidepressive treatment who remain clinically depressed, will be enrolled in an "Inflammation group" or in a "Non-inflammation group" depending on baseline levels of CRP. Subjects in both groups will receive EPA enriched omega-3 fatty acids for 8 weeks, added to their pre-stabilized antidepressant medication.