“A “double-blind randomized interventional study provide[d] first-time evidence that [extra long-chain omega-3s] exert positive effects on brain functions in healthy older adults,” a significant improvement in executive function after six and a half months of supplementation, and significantly less brain shrinkage compared to placebo.”

https://nutritionfacts.org/2019/08/27/vegans-should-consider-taking-dha-supplements/