Mental health benefits of Omega-3 fatty acids according to the existing research
Fish oil supplements are widely promoted and can easily be found in most supermarkets and health food stores. These polyunsaturated fats are considered “healthy” fats. There are 3 main types of Omega-3 fatty acids: alpha-linolenic acid (APA) found in foods like soybean and flaxseed and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) found in fish and seafood.
Omega-3 fatty acids improve various aspects of health. Proven to lower triglyceride levels (NIH healthcare reference), research also suggests that omega 3-fatty acids decrease the risk for developing breast cancer and dementia (NIH consumer reference). These health fats may also relieve symptoms of rheumatoid arthritis and delay the progression of macular degeneration (NIH complementary reference).
There is growing research on the positive effects of omega-3 fatty acids in mental health. In a systematic review of 35 randomized controlled trials of omega-3 fatty acids vs. placebo or antidepressant and fatty acids vs antidepressant alone, the formulations with high levels of EPA were found to be associated with decreased depressive symptoms (Hallahan, et al. study).
In a systematic review of 33 randomized controlled trials comparing omega 3- fatty acids vs. placebo in 1,848 patients, there was a small and modest improvement in depressive symptoms (Cochrane study). On a 52 point scale for depressive symptoms (see HAM-D), there was a 2.5 point decrease in symptom severity with the omega-3 fatty acids. A decreased score of 3 points is considered clinically relevant. Unfortunately, there is not enough data to recommend omega-3 fatty acids as a monotherapy and primary treatment for major depressive disorder.
There is research in the use of EPA as an adjunct treatment for major depression. A small study of 48 patients with major depressive disorder showed that the combination of EPA and 20mg of fluoxetine/Prozac decreased depressive symptoms more than EPA or fluoxetine alone (Jazayeri et al. study).
A study with 165 patients showed that an antidepressant (Escitalopram 10mg daily, Sertraline 100mg daily, or Fluoxetine 20mg daily) with 500mg omega-3 fatty acid supplementation improved depression scores more than antidepressants or the omega-3 fatty acids alone (DHA vs EPA was not differentiated in the report). The improvement in Hamilton depression severity scores were 4.6, 3.5, and 2.6 (Mehdi et al. study).
Another study of 144 depressed patients compared Sertraline 50mg daily and corn oil placebo pills to Sertraline 50mg daily and 930mg EPA-750mg DHA pills and found no difference in depression scores because both groups had improvement in their depressive symptoms (10 points on the Hamilton depression scale) (Carney et al.).
Omega-3 fatty acids are anti-inflammatory while omega-6 fatty acids are associated with inflammation (Wierenga and Pestka).
adapted from McHugh and Slavney 1998
An interesting study of 45 patients with obesity and a high level of C-reactive protein (CRP is a marker of inflammation) showed that high doses of EPA at 4gm/day decreased depressive symptoms by 50% or more in 64% of patients compared to 40% in placebo, 34% in EPA at 2gm/day, and 36% in EPA at 1gm/day. The high dose EPA group had the greatest decrease in both inflammation and depressive symptoms at 12 weeks (Mischoulon study).
There is no evidence that omega-3 fatty acids prevent the development of major depression (Okereke study).
There are 4 studies showing an increased risk in developing an arrhythmia called atrial fibrillation with increasing doses of omega-3 fatty acids (JAMA editorial). Patients with a cardiac history (ie coronary artery disease, heart failure) who are at increased risk for developing atrial fibrillation should not take high doses of omega-3 fatty acids (ie 4gm/day of EPA).
Besides some reports of nausea, upset stomach, and aversion to a “fishy” taste, there are no significant side effects from omega-3 fatty acid supplementation. Overall, increasing omega-3 fatty acid intake through diet (i.e. eating 2 servings of fatty fish like salmon per week) or fish oil supplementation is recommended for patients with major depression and high triglyceride levels or an inflammatory condition (e.g. rheumatoid arthritis). Psychotherapy and anti-depressant medications are still first-line treatments for major depression. EPA at an intermediate dose of 1gm/day can be considered as an adjunct for major depression treatment.