Can i take flaxseed oil 1000mg when i am on arimidex (anastrozole) and an antidepressant?

No direct conflict: Flax seed oil will not interact with arimidex. But there's some evidence that it can decrease platelet aggregation and increase bleeding time -- which some of the seritonergic antidepressants can do too. So if you're on one of those (like prozac, zoloft, (sertraline) celexa, etc) simply be mindful and report any unusual bruising if it happens. I'd suggest telling your doctors about the flaxseed oil also.