e thing is that the intervention in question doesn't have any specific antidepressant properties over and above the powerful antidepressant effects of placebo.
Placebo-controlled trials are the gold standard. But when enough of them have been done they can be lumped together into what is called a meta-analysis. In situations such as with omega-3s, where some studies are positive and some are negative, a meta-analysis sometimes allows a more accurate picture to arise.
There are two recent meta-analyses done of studies comparing omega-3 fatty acids with placebo, and even they don't agree with each other. The first, and smaller, meta-analysis found that overall omega-3 fatty acids were no more effective than placebo.
Moreover, the better quality each included study was, the less likely it was to be positive. This suggests the positive studies were mistakes.
A more recent, and larger, meta-analysis is a bit more optimistic. To make sense of its results you need to know that there are two types of omega-3 fatty acids that are most commonly used to treat depression: eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA. This meta-analysis found that only omega-3 preparations that were made of more than 60% EPA were effective for depression.
So a clear take-home message here is that if you do use an omega-3 fatty acid, make sure you get one that is mostly EPA.
CNN Comment Policy: CNN encourages you to add a comment to this discussion. You may not post any unlawful, threatening, defamatory, obscene, pornographic or other material that would violate the law. All comments should be relevant to the topic and remain respectful of other authors and commenters. You are solely responsible for your own comments, the consequences of posting those comments, and the consequences of any reliance by you on the comments of others. By submitting your comment, you hereby give CNN the right, but not the obligation, to post, air, edit, exhibit, telecast, cablecast, webcast, re-use, publish, reproduce, use, license, print, distribute or otherwise use your comment(s) and accompanying personal identifying and other information you provide via all forms of media now known or hereafter devised, worldwide, in perpetuity. CNN Privacy Statement.
The information contained on this page does not and is not intended to convey medical advice. CNN is not responsible for any actions or inaction on your part based on the information that is presented here. Please consult a physician or medical professional for personal medical advice or treatment.