Standardized mean differences in depressive symptoms in omega-3 PUFA-treated compared to placebo-treated subjects with major depressive disorder or bipolar disorder. SMD are the standardized mean differences (scaled to standard deviations) in the change-from-baseline scores in the placebo and treatment groups, along with 95% confidence intervals. A summary of each study's characteristics can be found in Table 4. All studies rated patients using the HDRS, except that conducted by Llorente and colleagues , which was therefore excluded from the analysis. I-squared is the proportion of variance attributable to the heterogeneity between studies, and the p-value is for Cohen's Q, a test of the statistical significance of that heterogeneity. The overall estimate is the inverse-variance-weighted average of the studies based on a random effects model.