The ideal ratio of Omega 6 to Omega 3 is 1:1. (Which is the ratio ingested by the Inuit of Greenland before their introduction of Western food. They ate almost no vegetable source food - almost all fish and sea products, and their vascular and cancer disease were almost zero.) Hemp oil has 3:1 and fish oil has 2:1. I buy my fish oil at Costco for $10 and it is from deep sea fish and is claimed to not have any toxins.
To receive anti-depressant benefits from Omega 3 you need a minimum of 3000 mg per day - which is 10 of the above pills per day. You can read about the benefits of Omega 3 for depression in the book "The Omega-3 Connection: The Groundbreaking Antidepression Diet and Brain Program." I've got several books on Omega 3 and they all recommend the fish oil, particularly over flax oil which I believe is 6:1. All clinical trials in relation to depression and also cardio vascular studies have been with the minimum of 3000 mg of Omega 3 from fish oil, and several of the studies were with double or more that amount. There are several clinical studies of the benefits and I personally go with the fish oil. There is also a prescription Omega 3 available but it is very pricey.