Compared to the control group (paraffin oil), the flaxseed oil group showed a significant increase in brain-derived neurotrophic factor concentration (1.12 ± 0.6 pg/mL vs. 0.2 ± 0.56 pg/mL; p < 0.0001) and a notable reduction in Beck Depression Inventory-II scores (−16.62 ± 7.03 vs. −8.45 ± 7.8; p < 0.0001) post-intervention. Here, BDNF is linked to major depressive disorder.