Objective: A decrease in omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFAs) and an increase in omega-6 (n-6) linoleic acid in the diet have been suggested as contributing factors in the pathogenesis of depression. The present study examined the relationship between red blood cell (RBC) n-3 and n-6 and serious psychological distress (SPD).
Methods: The authors analyzed data on 746 Inuit adults who took part in the 2004 Nunavik Inuit Health Survey. Fatty acids were quantified in RBC membranes. Psychological distress was measured by the Kessler 6-Item Scale (K6), a brief screening instrument for Diagnostic and Statistical Manual of Mental Disorders (fourth edition) mood disorders in the past 30 days. A score ≥13 on the K6 has been established as a threshold to differentiate cases of SPD from noncases.
Statistical analysis: The risk of SPD according to RBC n-3 and n-6 was assessed by logistic regression analysis. Weighted estimates were calculated by the SUDAAN statistical package to account for the complex survey design.
Results: The 30-day prevalence rate of SPD was 12.4%. In SPD cases, mean n-3 LC-PUFAs were lower (7.81% ± 0.24% [SEM] vs. 9.24% ± 0.12%, p < 0.0001) and mean total n-6 was higher (27.3% ± 0.36% vs. 25.9% ± 0.15%, p = 0.0003) than in noncases. For each 1% increase in RBC n-3 LC-PUFA, the odds ratio for SPD was 0.90 (95% confidence interval: 0.83, 0.99; p = 0.0248). However, neither individual n-6 FAs nor total n-6 was significantly associated (p ≥ 0.05) with SPD in multivariate analysis.
Conclusions: In this study, the authors observed that n-3 LC-PUFAs in RBCs were inversely associated with SPD. The study's cross-sectional design implies that one cannot ascertain any causal relationship. The findings suggest that n-3 LC-PUFA consumption from the traditional Inuit diet deserves prospective analyses.