The European Journal of Neuroscience published a study in 2013 showing that fish oil reversed all anxiety-like and depression-like behavior changes induced in rats. This is an interesting study because it stresses the importance of supplementing with fish oil at “critical periods of brain development.” (10) This is exactly why I recommend giving fish oil to our kids from early on to help them so they won’t develop anxiety or depression later in life.
A scientific review in 2014 evaluated study findings on omega-3 intake in relation to the prevention and treatment of breast cancer, the most prevalent cancer among women. The review found that EPA and DHA, as well as ALA, can differentially inhibit breast tumor development. According to this review, there is solid evidence to support the use of omega-3s as “a nutritional intervention in the treatment of breast cancer to enhance conventional therapeutics, or potentially lowering effective doses.” (16) Additionally, a 2016 study found that “very high fish consumption in early adulthood to midlife may be associated with decreased risk of breast cancer.” (17)
To evaluate the potential placebo effect, we made further subgrouping analyses. In the subgroups of studies using placebo controls, the omega-3 PUFAs still revealed a consistent positive anxiolytic association with anxiety symptoms. These phenomena meant that the anxiolytic effect of omega-3 PUFAs is probably not entirely owing to the placebo effect.
Among the 16 studies comparing the effect of omega-3 PUFA treatment with that of the placebo,33,34,36,47-49,51-53,55-61 the main results revealed a significantly greater association of treatment with reduced anxiety symptoms in patients receiving omega-3 PUFA treatment than in those not receiving it (k, 16; Hedges g, 0.372; 95% CI, 0.032-0.712; P = .03; eFigure 3 in the Supplement). The meta-analysis of the subgroup focusing on non–placebo-controlled trials also showed a significantly greater association of treatment with reduced anxiety symptoms in patients receiving omega-3 PUFA treatment than in those not receiving it (k, 3; Hedges g, 0.399; 95% CI, 0.154-0.643; P = .001).35,50,54

Jump up ^ Martins, Julian G (2009). "EPA but Not DHA Appears to Be Responsible for the Efficacy of Omega-3 Long Chain Polyunsaturated Fatty Acid Supplementation in Depression: Evidence from a Meta-Analysis of Randomized Controlled Trials". Journal of the American College of Nutrition. 28 (5): 525–42. doi:10.1080/07315724.2009.10719785. PMID 20439549.
An 18-month study was published in 2014 that evaluated how borage seed oil — rich in GLA — and fish oil rich fared against each other in treating patients with rheumatoid arthritis. It was discovered that all three groups (one taking fish oil, one taking borage oil and one taking a combination of the two) “exhibited significant reductions” in disease activity, and no therapy outperformed the others. For all three, “meaningful clinical responses” were the same after nine months. (11)
Fish oil can be obtained from eating fish or by taking supplements. Fish that are especially rich in the beneficial oils known as omega-3 fatty acids include mackerel, herring, tuna, salmon, cod liver, whale blubber, and seal blubber. Two of the most important omega-3 fatty acids contained in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Make sure to see separate listings on EPA and DHA, as well as Cod Liver Oil, and Shark Liver Oil.
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