This systematic review examined the effects of various plant-based compounds and phytonutrients—including ashwagandha, Rhodiola, St. John's Wort, cannabidiol, and curcumin—on the hypothalamic-pituitary-adrenal (HPA) axis in human clinical trials. While most phytonutrients yielded inconclusive results due to differences in study design and dosage, ashwagandha consistently demonstrated a reduction in morning cortisol
