More studies are also needed to determine the appropriate dosage and the best composition of omega-3 supplements, as well as the patients who are most likely to benefit from the therapy, Drs Pao-Yen Lin of Chang Gung University College of Medicine in Kaohsiung and Kuan-Pin Su of China Medical University Hospital in Taichung, both in Taiwan, conclude.
More fish, less depression
Fish and fish oil, as well as flax seed oil, are rich sources of omega-3 polyunsaturated fatty acids (PUFAs). Because areas in which there is high omega-3 PUFA consumption have a lower prevalence of depression, much interest has been generated in their use as antidepressants, the researchers note in the Journal of Clinical Psychiatry.
Interest has been particularly strong in using omega-3s for treatment-resistant depression, childhood depression, and postpartum depression. But studies to date have had mixed results.
Lin and Su reviewed 10 clinical trials, lasting four weeks or longer, which used two omega-3 PUFAs - eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) - to treat depression or bipolar disorder.
When the researchers pooled the data from all of the trials, they found a significant antidepressant effect of omega-3s.
Further research needed
However, because the trials used different methods to analyse the data, the researchers say the findings must be interpreted with caution. There is also evidence for publication bias, they add, meaning studies that didn't find a benefit of omega-3s were less likely to have been published than those with positive results.
Because omega-3s are safe and have many other health benefits, the nutrients could be particularly beneficial to patients with depression and heart disease or diabetes, or women who are pregnant or breastfeeding, Lin and Su note.
Nevertheless, they conclude: "more large-scale, well-controlled studies are warranted to find out the favourable target subjects, the optimal composition and the dosage of EPA and DHA, and the long-term efficacy of omega-3 fatty acids in treating depression." - (Reuters Health)
SOURCE: Journal of Clinical Psychiatry, July 2007.