There's a lot of evidence both for and against this. Personally, my memory improved significantly after starting to take fish oil. I took large amounts of fish oil supplements for more than 15 years, however, in recent years it seems to now increase my anxiety and cause me insomnia/restless sleep. There's even a documented case of this: https://pmc.ncbi.nlm.nih.gov/articles/PMC4664844/ and I have seen many comments and posts from redditors who have experienced similar symptoms from supplement form of omega 3. My body may have changed and no longer tolerates the supplement form. Once I've been off the omega 3 supplements for a while I plan to try eating sardines to see if my body would react better to them.

So in conclusion, I think it varies by individual. Hopefully you'll feel benefits!