Plain language summary
This study investigated whether Omega 3 (n-3) fatty acids had a clinical effect on five inflammatory biomarkers on individuals diagnosed with Major Depressive Disorder (MDD). Individuals were randomised into 3 groups, each of which took 8 weeks of double blind treatment with either eicosapentaenoic acid enriched n-3 fatty acids (EPA), docosahexaenoic acid enriched n-3 fatty acids (DHA), or placebo. There were no significant differences in the outcomes of the groups. However, it was noted that individuals with higher levels of inflammatory markers who took EPA improved more than those on placebo, and less on DHA than placebo. he larger the number of high inflammatory markers, the wider the gap between the improvements of the EPA versus placebo. Individuals with high hs-CRP, IL-6 or leptin responded less well to placebo than those with lower levels of these biomarkers. EPA was less effective than placebo or DHA if subjects had low levels of all 5 biomarkers. The five biomarkers were strongly influenced by gender and weight. The majority of obese women and men had at least one high marker of inflammation, and many of these had 2 high markers. There was no difference in treatment patterns for men and women. This is consistent with literature that suggests that inflammation is associated with obesity. Results suggest that it is important to look at more than one marker of inflammation, and that subjects with a specific combination inflammation markers were more likely to respond to EPA treatment. The authors concluded that anti-inflammation therapy was only beneficial for those with inflammation related MDD, and not helpful and possibly harmful for those with physiologically derived MDD.
Abstract
This study explores whether inflammatory biomarkers act as moderators of clinical response to omega-3 (n-3) fatty acids in subjects with major depressive disorder (MDD). One hundred fifty-five subjects with Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) MDD, a baseline 17-item Hamilton Depression Rating Scale (HAM-D-17) score ⩾ 15 and baseline biomarker data (interleukin (IL)-1ra, IL-6, high-sensitivity C-reactive protein (hs-CRP), leptin and adiponectin) were randomized between 18 May 2006 and 30 June 2011 to 8 weeks of double-blind treatment with eicosapentaenoic acid (EPA)-enriched n-3 1060 mg day(-1), docosahexaenoic acid (DHA)-enriched n-3 900 mg day(-1) or placebo. Outcomes were determined using mixed model repeated measures analysis for 'high' and 'low' inflammation groups based on individual and combined biomarkers. Results are presented in terms of standardized treatment effect size (ES) for change in HAM-D-17 from baseline to treatment week 8. Although overall treatment group differences were negligible (ES=-0.13 to +0.04), subjects with any 'high' inflammation improved more on EPA than placebo (ES=-0.39) or DHA (ES=-0.60) and less on DHA than placebo (ES=+0.21); furthermore, EPA-placebo separation increased with increasing numbers of markers of high inflammation. Subjects randomized to EPA with 'high' IL-1ra or hs-CRP or low adiponectin ('high' inflammation) had medium ES decreases in HAM-D-17 scores vs subjects 'low' on these biomarkers. Subjects with 'high' hs-CRP, IL-6 or leptin were less placebo-responsive than subjects with low levels of these biomarkers (medium to large ES differences). Employing multiple markers of inflammation facilitated identification of a more homogeneous cohort of subjects with MDD responding to EPA vs placebo in our cohort. Studies are needed to replicate and extend this proof-of-concept work.
Methodological quality
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