Fish oil may also prevent Alzheimer's dementia. This is currently being investigated at Columbia.
as for its benefits in mood disorders...
http://www.ncbi.nlm.nih.gov/sites/entrez
http://abcnews.go.com/WNT/MedicineCuttingEdge/story?id=129498&page=1
Plenty of hits. Overall there are some studies not showing efficacy, but several that do. IMHO its enough to justify suggesting to a patient to consider the use of fish oil as an adjunctve treatment in addition to an FDA approved antidepressant, not a replacement for such, and if you suggest its use, do tell the patient that more research needs to be done. I personally suggest it because many of my patients have problems that fish oil may help such as high blood pressure & hyperlipidemia, and is well tolerated & cheap. If I got the time I also suggest a well balanced diet. I also am mindeful that fish oil is an anti-platelet agent just like SSRIs are. While they are not very strong antiplatelet agents, consider this and consider that patients may be on other anti-platelet/anti-coagulant agents.
Also from the MGH Psychiatry Update & Board Prep book...
One Carbon Cycle Metabolism Abnormalities-S-adenosyl methionine, folate, Vit B12 & homocysteine are linked with depression. High homocysteine, low folate, low Vit B12 & low SAM-E are linked to depression.
I would reccomend against the use of St. John's Wort. For the reasons mentioned above but also becuase it has more side effects than conventional meds & has less efficacy. In fact some studies show no effect at all. Lots of people have an erroneous idea that just because something is "natural" its safer & better. True in some cases, not true in others. This is a case where its not true.