What Are the Benefits of Fish Oil for Depression?
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More than 17 million adults had an episode of depression in 2017 (the most recent data available), according to the National Institute of Mental Health. Right now, the strain on mental health is only getting worse, according to a study published in September 2020 in JAMA Network Open; people reported symptoms of depression at three times the rate they did before the pandemic.
And while there’s no one-size-fits-all approach guaranteed to ease depression, the good news is that researchers know a lot about what works to help with symptoms (including sadness, hopelessness, and an inability to enjoy the things you once did). And there’s a lot of ongoing research about complementary therapies that may also help, including fish oil.
What We Know About the Fish Oil–Mental Health Connection
Fish oil, the fat that comes from fish and seafood, contains two types of omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), according to the National Center for Complementary and Integrative Health. A third omega-3 fatty acid, alpha-linolenic acid, is found in plant sources, like walnuts, flax, and chia. While the body needs all three omega-3s, EPA and DHA appear to have some of their own benefits. It’s important to keep in mind that the terms “omega-3 fatty acids,” “fish oil,” and “fish oil supplements” are related but cannot necessarily be used interchangeably.
Numerous studies suggest that a deficiency in omega-3s is linked to an increased risk of several psychiatric disorders, including depression, bipolar disorder, and dementia. That’s prompted researchers to investigate if fish oil — and the EPA and DHA in it — can help prevent or treat the various mental health conditions it’s been linked with, according to a review published in March 2020 in the Global Health Journal.
“We know the brain is made up of a lot of fat, and healthy fats seem to be good for the brain. However, one issue is that we can’t get inside of people’s brains to actually know what the omega-3 is doing,” says Philip R. Muskin, MD, professor of psychiatry in Columbia University’s department of psychiatry in New York City.
Evidence does suggest that omega-3s can travel through the cell membranes of brain cells and interact with molecules known to play a role in mood regulation, according to Harvard Health Publishing. More specifically, one theory is that the anti-inflammatory properties of the omega-3s found in fish oil help stabilize mood.
There are some indications that depression involves inflammation in different parts of the nervous system, according to research published in 2019 in Frontiers in Immunology. “And omega-3s reduce a variety of inflammatory products, including tumor necrosis factor and interleukin-2, -6 , and -1 beta,” Dr. Muskin says. It may be that this anti-inflammatory process helps regulate mood.
That said, people can become depressed without having excessive inflammatory activity, says David Mischoulon, MD, PhD, a psychiatrist and the director of the depression clinical and research program at Massachusetts General Hospital in Boston. “Inflammation is not the only pathway to depression, but we think it is a contributor.”
What Does the Science Say About Fish Oil for Depression?
Overall, more research is needed, but studies done so far are promising.
A significant body of work has been done on fish oil as both an add-on treatment and a stand-alone treatment for depression, says Dr. Mischoulon. “By and large, studies collectively support that taking omega-3s is effective and safe,” he says.
The problem is that there’s a lot of variability in how studies have been designed, in terms of dosing, the size of the study, and the source and formulation of the fish oil itself, so the conclusions of the research should be interpreted somewhat cautiously, Mischoulon explains. “There isn’t a clear idea of the optimal preparation or dose,” he says.
What’s more, some studies that didn’t show a benefit may have been pulling from a population of people with depression who didn’t have high levels of inflammation to begin with — and therefore wouldn’t see a benefit from the anti-inflammatory effects of fish oil. (The reverse could also be true.)
There is evidence that people who eat more fish have an 11 percent lower risk of developing depression compared with people who eat less fish, according to a systematic review and meta-analysis of 10 prospective studies published in December 2018 in the journal Asia-Pacific Psychiatry. A separate review and meta-analysis published in November 2016 in the Journal of Affective Disorders suggests that consuming 0.6 grams of EPA and DHA from fish is associated with a lower risk for the mood disorder (3 ounces of salmon contains about 1.5 to 1.75 grams of EPA and DHA, per the National Institutes of Health).
And when it comes to supplements, researchers concluded in a review published in December 2017 in the Journal of Integrative Neuroscience that based on clinical trials comparing a placebo to a fish oil supplement, the supplement was effective in helping treat depression symptoms but was best used as an add-on treatment to traditional prescription antidepressant medications rather than by itself. According to the trials reviewed, there were no serious side effects linked to taking the supplements.
A recent meta-analysis published in May 2020 in BMC Psychiatry looked at 10 randomized, controlled trials of 910 people with depression who took either omega-3 supplements or a placebo; it concluded that both high- and low-dose EPA and DHA supplements were more effective compared with a placebo in relieving symptoms, and this effect was greatest during the early stages of depression.
Despite this promising evidence, it’s still important to keep in mind that research has yet to define the specific role that fish oil should play in mental health care, says Ken Duckworth, MD, chief medical officer at the National Alliance on Mental Illness.
Nondrug, lifestyle behaviors like practicing self-care, eating a healthy diet, exercising, and socializing have much more evidence to show they help with mood. “I wouldn’t begin with fish oil,” Dr. Duckworth says. “Fish oil is not a cure-all for mood disorders.”
Is Fish Oil an Antidepressant?
It’s not clear yet, based on current data, whether fish oil can work as an antidepressant, Muskin says.
Antidepressants drugs act on chemicals in the brain thought to affect mood such as serotonin, norepinephrine, and dopamine. Fluoxetine (Prozac) is a common selective serotonin reuptake inhibitor medication that treats depression. Although it is not yet clear how antidepressants work, this drug can increase the amount of serotonin in the synapses between brain cells (how brain cells communicate). Serotonin has many actions throughout the body, but in the brain it is thought to play a role in mood, appetite, and sleep, among other things.
While there is research suggesting that fish oil may improve symptoms of depression, studies have not yet shown how it acts on the neurotransmitters in the brain, or even if it does. So it’s impossible to know if fish oil acts similarly as antidepressants, Muskin says.
So Do Doctors Recommend Fish Oil — or Other Omega-3s — for Depression?
The short answer is not regularly, at least not yet. The long answer is a bit more complicated. Depending on your own risks of depression and other health conditions, your physician may recommend fish oil supplements.
Muskin and Mischoulon both say they recommend fish oil supplements to some patients because of their diet and overall health needs. But again, this recommendation does not apply to everyone.
Eating fish is widely recommended as part of a healthy diet. (The most recent Dietary Guidelines for Americans from the U.S. Department of Agriculture recommends that U.S. adults eat 8 ounces of fish per week.)
If you and your doctor determine it is a good idea to try a fish oil supplement, know that there is no conclusive evidence on an optimal dose. Based on your diet and personal history, your doctor can help you determine the best dose for you.
What Type of Omega-3s or Fish Oil May Be Best for Depression?
In choosing a specific fish oil supplement for depression, it’s important for you and your doctor to consider how much EPA and DHA it contains.
A meta-analysis published in September 2019 in Psychotherapy and Psychosomatics, for which Mischoulon was a coauthor, suggests that supplements with a 2 to 1 or higher ratio of EPA to DHA and 1 to 2 total grams of EPA are effective, based on prior data. Other research suggests that EPA is a more potent anti-inflammatory when it comes to depression, according to data published in January 2016 in Molecular Psychiatry.
However, the amount of DHA and EPA that a fish oil supplement contains is not always easy to find out as a consumer. Some reputable, high-quality brands present this information on the label or their website, but others list just the total omega-3s.
And remember: Dietary supplements are not tested by the Food and Drug Administration before being marketed to consumers, so it’s important to research the brand. Muskin advises looking for fish oil supplements that are made from fish oil from small fish like anchovies and sardines; free of contaminants like mercury; and transparent about fillers and ingredients used to make the encasing, like gelatin, soy, or lactose, in case you have an allergy or intolerance.
As for how much to take, that is best left up to your doctor. Muskin notes that more is not necessarily better when it comes to taking fish oil for mental health and may quickly become unnecessarily expensive.
What is clear is that if you are concerned that you have depression, don’t try to treat it yourself with any therapy, including fish oil. Talk to your primary care doctor to start; they can screen you for depression and then determine the appropriate treatment for you.