Fish and fish oil are regarded as one of the best additions to a healthy diet because of their immense nutritional qualities. Fish and fish oil supplements have also proven very effective for treating depression and other mental health disorders. Research shows that depression is less common in nations where people eat large amounts of fish.
Why Are Fish Oils So Good For Depression?
Besides being a great source of protein, fish contain omega-3 polyunsaturated fatty acids (PUFA), an essential nutrient in the structure of every cell in the human body.
The latest research shows multiple benefits of omega-3 for both physical and mental health.  Two omega-3 fatty acids — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) — are thought to have the most benefit for people with depression and mood disorders.
The first news about the connection of omega-3 and depression gained attention in 1998 when a researcher noted that patients suffering from depression had significantly lower omega-3 levels in the red blood cells. [Source: WebMD]
Since then, many studies have discussed the deficiency of omega-3s as an increased risk of mental health disorders such as bipolar disorder , depression, and dementia – prompting researchers to investigate if fish oils can help improve psychiatric disorders and other mental conditions. [Source: ScienceDirect]
Omega-3s can be added to the diet in different forms:
- Consuming fish oil supplements
- Taking flaxseed oil
- Taking algae oil
As stated earlier, fish oils offer various health benefits; these include:
- Improves skin health
- Lowers blood pressure
- Reduces triglycerides
- Improves cardiac health
- Enhances cognitive function
- Improves mental health disorders
Now, let’s take a closer look at the mental health benefits of consuming fish oils: =
Reduces Inflammation 
The latest research shows that depression is an inflammatory disease. Psychiatrist and director of the depression clinical and research program at Massachusetts General Hospital, David Mischoulon, MD, Ph.D., says:
“Inflammation is not the only pathway to depression, but we think it is a contributor.”
Since omega-3s can lower inflammation, it is proven to be beneficial for depression. According to research published in 2019 in Frontiers in Immunology, omega-3s reduce various inflammatory products like tumor necrosis factor and interleukin-2, -6, and -1 beta (anti-inflammatory processes that help regulate mood).
Multiple factors contribute to the etiology of depression, including an imbalance in the neurotransmitters serotonin and dopamine. Consuming omega-3 enhances the regulation of serotonin and dopamine transmission, thus improving mood and symptoms of depression. [Source: PubMed]
According to the May 1999 Archives of General Psychiatry, Andrew Stoll reported a study of fish oil in 30 manic-depressive patients. 64% of patients that took 10 grams of fish oil per day for four months showed significant improvements, whereas only 19% of those receiving the placebo benefited. [Source: WebMD]
Over 30 clinical trials have tested the omega-3 and depression link. Studies have used omega-3s as an add-on therapy for depression patients taking prescription antidepressants. Other studies have examined omega-3 therapy alone. Most of these clinical trials use EPA or a combination of EPA and DHA. The result showed conclusive evidence that omega-3 consumption improved depressive symptoms. [Source: Harvard]. 
Meta-analyses suggest that omega-3s are an effective treatment for people suffering from depression. The most effective dosage appears to be at least 60% EPA relative to DHA. While DHA is less effective as an antidepressant, it may have protective effects against suicide [Source: Medscape].
A recent meta-analysis examined 10 randomized controlled trials of around 1000 people with depression who took either omega-3 supplements or a placebo. The study reported that omega-3 supplements (both high- and low-doses) were more effective in relieving depressive symptoms than the placebo. [Source: BMC Psychiatry]
Do Doctors Recommend Fish Oils for Depression?
Yes, depression or not, doctors do recommend consuming fish oils for optimal physical and mental health. Dietary Guidelines for Americans from the U.S. Department of Agriculture recommends 8 ounces of fish per week for adults.
Moreover, the U.S Food and Drug Administration (FDA) recommends eating 2-3 servings of fish every week. 4 ounces per serving for adults and 2 ounces for children.
A 2019 meta-analysis by Mischoulon in Psychotherapy and Psychosomatics shows that fish oil supplements with a higher ratio of EPA to DHA are more effective. Other research suggests EPA be more potent when it comes to depression, according to data published in Molecular Psychiatry in 2016. [Source: WebMD]
Depending on the risks and symptoms of depression or other health conditions, your physician may recommend fish oil supplements.
What Dose of Fish Oil is Beneficial?
Fish oil (or omega-3) dosages for depression can range from >1g/day to 3g/day. If your doctor determines that it is good to start fish oil supplements, he will set the dosage based on your diet and personal history.
- Omega-3 fatty acids and the treatment of depression: a review of scientific evidence by Ab Latif Wani, Sajad Ahmad Bhat, and Anjum Ara. 2015. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481805
- Omega-3 for bipolar disorder: meta-analyses of use in mania and bipolar depression by Jerome Sarris, David Mischoulon, Isaac Schweitzer. 2011. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/21903025/
- Omega-3 Fatty Acids Could Reduce Depression Symptoms Through Anti-Inflammatory Effects: https://www.pharmacytimes.com/view/omega-3-fatty-acids-could-reduce-depression-symptoms-through-anti-inflammatory-effects
- Fish oil and depression: The skinny on fats by Mansoor D. Burhani and Mark M. Rasenick. 2018. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6087692/
- Efficacy of omega-3 PUFAs in depression: A meta-analysis. Retrieved from: https://www.nature.com/articles/s41398-019-0515-5
- Omega-3 fatty acids and mental health: https://www.sciencedirect.com/science/article/pii/S241464472030004X
- Omega-3 Dose Was Likely a Factor in Recent Anxiety & Depression Study Review: https://omegaquant.com/omega-3-dose-was-likely-a-factor-in-recent-anxiety-and-depression-study/
- Omega-3 and Depression: https://www.healthline.com/health/omega-3-depression
- Fish Oils Supplements can Improve Depression: https://www.mayoclinic.org/diseases-conditions/depression/expert-answers/fish-oil-supplements/faq-20058143
- Omega-3 Fatty Acid For Mood Disorders: https://www.health.harvard.edu/blog/omega-3-fatty-acids-for-mood-disorders-2018080314414
- What Are The Benefits of Fish Oil For Depression: https://www.everydayhealth.com/diet-nutrition/what-are-the-benefits-of-fish-oil-for-depression/
- omega-3 Fatty Acid For Mood Disorders: https://www.health.harvard.edu/blog/omega-3-fatty-acids-for-mood-disorders-2018080314414
- Fish Oil and Depression: https://consumer.healthday.com/encyclopedia/depression-12/depression-news-176/fish-oil-and-depression-644950.html