Phenolic acids, a class of plant-derived polyphenols found in foods such as coffee, fruits, and vegetables, have attracted attention for their potential role in supporting mood and treating depression. Scientific interest stems from their antioxidant and anti-inflammatory properties, which are relevant because oxidative stress and inflammation have been linked to the pathophysiology of depression. Preclinical studies in animal models suggest that specific phenolic acids, such as ferulic acid, caffeic acid, and gallic acid, may exert antidepressant-like effects. These effects are thought to be mediated through modulation of neurotransmitter systems, reduction of neuroinflammation, and enhancement of neurogenesis in the hippocampus.

However, human clinical evidence is limited. Some observational studies suggest that diets rich in polyphenols, including phenolic acids, are associated with a lower risk of depression. A few small interventional studies and meta-analyses have shown modest improvements in mood with polyphenol-rich interventions, but these studies often do not isolate phenolic acids from other polyphenols, making it difficult to determine their unique effects.

In summary, while there is a scientific rationale and preliminary evidence from laboratory and animal studies, high-quality human clinical trials specifically examining phenolic acids for depression are lacking. Thus, the evidence supporting their use for depression is modest (rated 2/5).