DHA and EPA
<p>Omega-3 fatty acids, given in the form of fish oil tablets, were shown in a 1999 controlled trial<a href="http://www.ncbi.nlm.nih.gov/pubmed/10232294"><sup>Stoll</sup></a><sup> </sup>to maintain mood stability far better than an olive oil placebo. This was a very exciting result, especially as the trial was inspired by "bench chemistry" -- omega-3 fatty acids were recognized to have intracellular effects similar to lithium and valproate. Now some other small studies are beginning to be reported.
There are two "omega-3" fatty acids in fish oil: EPA (eicosapentaenoic) and DHA (docusahexaenoic). Some studies in people with depression or bipolar disorder have used EPA alone, including one of the most recent with the strongest positive results; but one of the larger earlier studies using EPA alone showed no benefit. Many of the other studies shown below, including the first one from Harvard, used fish oil tablets which provided both EPA and DHA. For now it seems safe to conclude that having both does not interfere with the antidepressant and mood stabilizing actions; and that EPA alone <i>might</i> be sufficient.
You may have heard of omega-3's or fish oil as having some benefit in reducing heart disease as well. That research is a little farther along than the mood research. I have not followed it closely but it seems that the focus there is more on DHA than EPA. This means that if you want <i>both </i>benefits, you may need to stick with a source that has both EPA and DHA. Luckily, it turns out that the cheapest version has both, and has been lowest in the tests of mercury (undetectable levels). </p>
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So for now it looks like the cheapest source may be the best -- an unusual situation in my business! Details on which kind to consider, and how many pills you'll need, can be found on the <a href="http://www.psycheducation.org/depression/meds/fishoilscraps.htm">"more fish (oil) stories"</a> page. For another excellent source of information, a bit more technical but more complete, see the <a href="http://www.mayoclinic.com/health/fish-oil/NS_patient-fishoil">Mayo Clinic pages</a> on omega-3 fatty acids. </p>