Does omega-3 prevent postpartum depression?
Omega-3 supplements have not been shown to prevent postpartum depression, and the evidence supporting their use as a treatment is also still too weak for a recommendation. If you experience symptoms of low mood after giving birth, seek professional help rather than relying on supplements.
Omega-3 supplements have not been shown to prevent postpartum depression in healthy women. Several large analyses, including a Cochrane review, found no statistically significant preventive effect of DHA- or EPA-rich fish oil compared with a placebo. The effect size was close to zero.
For the treatment of an already existing postpartum or pregnancy-related depression, the picture is somewhat less clearly negative. An analysis of eighteen studies (over 4,000 women) found a small benefit in women who were already depressed. However, outcomes varied considerably between studies and the confidence intervals were wide, making it difficult to draw firm conclusions.
One analysis looked specifically at supplements with a higher ratio of EPA relative to DHA (EPA/DHA 1.5 or higher). In women with mild to moderate depression during or after pregnancy, this appeared to work slightly better than a neutral ratio. Side effects (mild gastrointestinal complaints) were no more frequent than with placebo. However, this is based on a limited number of small studies.
In a randomised trial involving 59 women with severe perinatal depression, in which all participants also received psychotherapy, no added benefit of omega-3 (1.9 grams EPA+DHA per day) over placebo was found. Both groups improved, most likely largely due to the therapy. The researchers themselves noted that the small sample size and short duration may have made it possible to miss an effect.
If you experience symptoms of low mood during or after your pregnancy, discuss this with your doctor or midwife. Omega-3 is safe during pregnancy and has other benefits for the foetus, but as a remedy for postpartum depression the evidence to date is too weak to rely on.
This answer is based on multiple systematic analyses of randomised studies, including a Cochrane review. The evidence is strongest for the conclusion that omega-3 has no preventive effect: that finding is consistent across the largest and most rigorous analyses. The evidence for a therapeutic effect in already existing depression is less clear-cut and comes from studies that differed substantially from one another. The researchers behind a central analysis themselves acknowledge as a limitation that the sample sizes may have been too small, the study duration too short, and the dose too low to demonstrate or rule out a real effect. This means that "no effect found" is not the same as "definitely does not work," but it also means there is currently no reason to recommend omega-3 as a preventive measure.