Criteria for Inclusion of Studies in this Review
Studies were included in this meta-analysis if they were (1) randomized, placebo-controlled trials examining the efficacy of omega-3 fatty acids in adults with MDD. Trials were considered randomized when investigators explicitly represented them as such in the methods section of their published manuscript. Trials examining the efficacy of omega-3 fatty acids in treating MDD in subjects with medical comorbidity (i.e. cardiac disease, Parkinson's disease) or pregnancy were included in this meta-analysis. Trials were included if they examined the efficacy of omega-3 fatty acids to target depressive symptoms (as a primary outcome) in patients who may not have received a formal psychiatric diagnosis (i.e.in a primary care setting). Trials examining the efficacy of omega-3 FAs in treating depressive symptoms in the context of another primary psychiatric disorder, such as bipolar disorder or schizophrenia, were not included. Trials in which pharmacological agents of known efficacy were started at the same time as omega-3 fatty acids were also excluded.