Associations of n-3 polyunsaturated fatty acid status and intake with paediatric major depressive disorder in Swiss adolescents: A case-control study

Background: Observational studies suggest a link between n-3 polyunsaturated fatty acid (PUFA) intake, n-3 PUFA status, and depression in adults, but studies in adolescents are scarce. This study aimed to determine associations of n-3 PUFA status and intake with paediatric major depressive disorder (pMDD) in Swiss adolescents.Methods: We conducted a matched case-control study in 95 adolescents diagnosed with pMDD and 95 healthy controls aged 13 to <18 years. We analysed red blood cell (RBC) fatty acid (FA) composition (% of total FA). n-3 PUFA intake was assessed using a focused food frequency questionnaire and depression severity was assessed by the Children's Depression Rating Scale-Revised (CDRS-R).Results: Mean RBC eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were lower in cases than controls (EPA: 0.41 & PLUSMN; 0.11 vs 0.46 & PLUSMN; 0.12, p < 0.001; DHA: 4.07 & PLUSMN; 1.04 vs 4.73 & PLUSMN; 1.04, p < 0.001). Subsequently, the mean RBC n-3 index was lower (4.51 & PLUSMN; 1.10 vs 5.20 & PLUSMN; 1.11, p < 0.001) and the n-6/n-3 PUFA ratio higher (5.51 & PLUSMN; 1.25 vs 4.96 & PLUSMN; 1.08, p < 0.001) in cases than controls. Adolescents with a higher n-3 index had lower odds for depression (OR = 0.49 [95% CI: 0.32-0.71]). In contrast, the n-6/n-3 PUFA ratio was associated with higher odds for depression (OR = 1.58 [95% CI: 1.14-2.25]). Intake of alpha-linolenic acid, EPA and DHA did not differ between cases and controls.Conclusion: Our results suggest that a higher RBC n-3 PUFA status during adolescence is associated with a lower risk for pMDD, whereas a higher n-6/n-3 PUFA ratio is associated with a higher risk for pMDD. Differences in n-3 PUFA intake did not explain the observed differences in n-3 PUFA status.