Eicosapentaenoic acid (EPA) is an omega-3 polyunsaturated fatty acid found primarily in fish oil. Its use in supporting or treating Post-Traumatic Stress Disorder (PTSD) is rooted in scientific inquiry, though the evidence is limited and not yet definitive. Several small randomized controlled trials (RCTs) and observational studies have explored the impact of omega-3 fatty acids, specifically EPA, on symptoms of PTSD, given the role of inflammation and neurochemical changes in this condition.

Some studies suggest that EPA supplementation may help reduce PTSD symptoms, possibly due to its anti-inflammatory effects and influence on neurotransmitter pathways involved in mood regulation. For example, a 2011 pilot study by Matsuoka and colleagues found that high-EPA supplementation reduced PTSD symptoms in accident survivors. However, these studies tend to be small, have methodological limitations, and often combine EPA with other omega-3 fatty acids like DHA, making it hard to isolate EPA's specific effects.

Meta-analyses and systematic reviews of omega-3 supplementation for psychiatric disorders, including PTSD, generally conclude that while there is some promise, the quality of evidence is low, and larger, well-designed clinical trials are needed. Major guidelines do not currently recommend EPA as a primary treatment for PTSD. Thus, the evidence supporting EPA for PTSD is scientific but weak, meriting a low evidence score.