The short version
In the 2021 Cochrane review, omega-3s beat placebo for major depression by about 2.5 points on the Hamilton scale, below the 3 points that counts as clinically meaningful. Certainty was very low.
Only 1 small trial compared omega-3s directly with an antidepressant. Most of the evidence tests fish oil alongside treatment, not instead of it.
Stopping an antidepressant without the prescriber's help can bring withdrawal symptoms and a return of depression.
Your job is to affirm the question, explore what is behind it, and help the client take it to their prescriber.
What the evidence shows
Appleton et al. (2021) updated the Cochrane review of omega-3 fatty acids for major depression in adults. Across 33 placebo-controlled trials (1,848 people), omega-3s produced a small benefit, equal to about 2.5 points on the 17-item Hamilton Depression Rating Scale. The smallest change considered clinically important on that scale is 3 points, so the authors judged the effect unlikely to be clinically meaningful. The confidence interval ran from a possibly important effect to a negligible one, the trials varied considerably, and the authors found signs the estimate may be biased in favor of omega-3s. There was no difference in remission or response rates. Certainty was low to very low.
The question your client is asking, fish oil instead of medication, was tested in exactly 1 trial of 40 people. It found no difference, but the confidence intervals were so wide that, in the review's words, they "do not rule out important beneficial or detrimental effects of n-3PUFAs compared to antidepressants."
Most of the trials studied fish oil as an add-on. In a meta-analysis of 26 placebo-controlled trials by Liao et al. (2019), 10 enrolled people who were taking antidepressants and 8 more enrolled a mix of people on and off them (counted from the study's characteristics table). That evidence describes fish oil alongside treatment. It says nothing reassuring about stopping treatment.
Prevention doesn't look better. VITAL-DEP (Okereke et al., 2021) randomized 18,353 adults aged 50 and older to 1 g/day of fish oil or placebo for a median of 5.3 years. Mood scores did not differ, and depression risk was slightly higher in the fish oil group (hazard ratio 1.13). The authors concluded the findings "do not support the use of omega-3 supplements in adults to prevent depression."
Why the decision stays with the prescriber
Stopping is not a neutral act. The NHS (2025) advises, "Do not stop taking an antidepressant suddenly or without talking to your doctor first." It lists withdrawal symptoms such as dizziness, sleep problems, a racing heart, and feeling low or suicidal, and notes they can be severe and last months for some people. A prescriber plans a gradual reduction, usually over weeks or months. The National Institute of Mental Health (NIMH, 2023) says people should not stop a prescribed medication, even if they feel better, without a health care provider's help, and that stopping too soon may cause unpleasant or harmful side effects.
Both halves of the client's question sit outside coaching scope. The NBHWC Scope of Practice says coaches do not "prescribe or de-prescribe" or "recommend supplements" (National Board for Health & Wellness Coaching [NBHWC], n.d.). What you can do, with permission, is share information from nationally recognized authorities like NIMH.
Using it with clients
The question usually carries something worth hearing: side effects, cost, a wish for something "natural," worry about being on medication long term, or feeling well enough to wonder if they still need it. Start there.
Affirm: "You're thinking carefully about what you put in your body. That makes sense."
Explore: "What has you thinking about switching?"
Reflect: "Part of you is tired of the side effects, and part of you doesn't want to slide back to how things were."
Ask permission: "Would it be okay if I shared what the research says about fish oil and depression?"
If they say yes, keep it short: a small and uncertain effect, mostly tested alongside medication, with almost no research on replacing it. Add that NIMH advises against stopping without the prescriber's help.
Then turn to the prescriber as a partner, not a gatekeeper: "This is exactly the kind of question your prescriber can work through with you. What would you want to ask them?" Planning that conversation is coaching. The client can write down their reasons, list their side effects, and mention any supplements they already take, which NIMH also recommends telling providers about. If the client has already stopped, encourage them to contact their prescriber soon.
If a client mentions thoughts of suicide or self-harm, set the session agenda aside, stay with them, and connect them to help right away. In the US, they can call or text 988 or chat at 988lifeline.org to reach the 988 Suicide & Crisis Lifeline, which is free, confidential, and available 24/7. In life-threatening situations, call 911 (NIMH, 2026). Then follow the crisis protocol in your coaching agreement.
Where coaching stops
Coaches don't advise starting, stopping, or tapering any medication, and don't recommend for or against supplements or doses. Medication changes belong with the prescriber. Questions about combining a supplement with a medication go to the prescriber or a pharmacist. Worsening mood or a need for therapy goes to a mental health professional. Any mention of suicide or self-harm gets an immediate referral, as above.
Go deeper
The Evidence Literacy for Coaches package, which covers how to read supplement claims, is in development, along with Professional Practice and Settings, which covers scope and referral.
References
988 Suicide & Crisis Lifeline. (n.d.). 988 Suicide & Crisis Lifeline. Retrieved November 1, 2026, from https://988lifeline.org/
Appleton, K. M., Voyias, P. D., Sallis, H. M., Dawson, S., Ness, A. R., Churchill, R., & Perry, R. (2021). Omega-3 fatty acids for depression in adults. Cochrane Database of Systematic Reviews, 2021(11), CD004692. https://doi.org/10.1002/14651858.CD004692.pub5
Liao, Y., Xie, B., Zhang, H., He, Q., Guo, L., Subramanieapillai, M., Fan, B., Lu, C., & McIntyre, R. S. (2019). Efficacy of omega-3 PUFAs in depression: A meta-analysis. Translational Psychiatry, 9(1), 190. https://doi.org/10.1038/s41398-019-0515-5
National Board for Health & Wellness Coaching. (n.d.). Scope of practice. Retrieved November 1, 2026, from https://nbhwc.org/wp-content/uploads/2026/08/Scope-of-Practice-PDF.pdf
National Health Service. (2025, June 12). Antidepressants. https://www.nhs.uk/mental-health/talking-therapies-medicine-treatments/medicines-and-psychiatry/antidepressants/overview/
National Institute of Mental Health. (2023, December). Mental health medications. https://www.nimh.nih.gov/health/topics/mental-health-medications
National Institute of Mental Health. (2026, August). Suicide prevention. https://www.nimh.nih.gov/health/topics/suicide-prevention
Okereke, O. I., Vyas, C. M., Mischoulon, D., Chang, G., Cook, N. R., Weinberg, A., Bubes, V., Copeland, T., Friedenberg, G., Lee, I.-M., Buring, J. E., Reynolds, C. F., III, & Manson, J. E. (2021). Effect of long-term supplementation with marine omega-3 fatty acids vs placebo on risk of depression or clinically relevant depressive symptoms and on change in mood scores: A randomized clinical trial. JAMA, 326(23), 2385–2394. https://doi.org/10.1001/jama.2021.21187
